The research, published in Frontiers in Medicine, followed 963 episodes of complicated urinary tract infection caused by Enterobacterales, the family of gut bacteria that includes Escherichia coli and Klebsiella pneumoniae. Between March 2024 and March 2026, the team at Misurata University and four local hospitals collected 1,017 bacterial isolates in real time, identified them with biochemical panels and MALDI-TOF mass spectrometry, and subjected each to a battery of phenotypic tests for beta-lactamase enzymes and biofilm formation. It is one of the most detailed clinical-microbiological datasets yet assembled from a North African setting that is chronically underrepresented in the infection literature.

The resistance burden they documented is sobering in its own right. More than half of the isolates qualified as multidrug-resistant. Roughly 37 percent produced extended-spectrum beta-lactamases (ESBLs), enzymes that disable penicillins and most cephalosporins. About 18 percent carried AmpC-type enzymes, concentrated in species such as Enterobacter cloacae and Citrobacter freundii, and around one in ten produced carbapenemases, the enzymes that undermine the last-line carbapenem antibiotics. Biofilm formation — the ability to coat surfaces in a protective matrix — was detected in 72 percent of isolates. On paper, these bacteria look formidable.

Yet when the researchers ran the numbers, phenotype after phenotype fell away. In a multivariable logistic regression adjusted for age, sex, hospital, catheterization, prior antibiotics, comorbidities and more, isolates producing two or more beta-lactamase categories showed no significant independent association with treatment failure. Multidrug resistance itself was likewise not independently linked to failure. The adjusted odds ratios hovered near or below one, with confidence intervals that straddled the null in most sensitivity analyses.

What did matter were three clinical factors. Urinary obstruction raised the odds of failure by about 55 percent, diabetes by roughly 48 percent, and sepsis by nearly 60 percent. A separate model examining source control — the surgical or procedural correction of the underlying problem, such as draining an obstructed kidney or swapping an infected catheter — found that when source control was needed but inadequate, the odds of failure roughly doubled compared with cases needing no intervention. The message is physiologically coherent: antibiotics cannot sterilize a plumbing system that remains blocked, and a septic patient has far less reserve to tolerate any delay.

One result was genuinely unexpected. Biofilm-positive infections appeared to fare slightly better, with an adjusted odds ratio of 0.70 in the primary model — an inverse association that seems to contradict decades of laboratory work linking biofilms to persistence and antibiotic tolerance. The authors are emphatic that this should not be read as biofilm being protective. The finding flickered in and out of statistical significance across sensitivity analyses and vanished entirely when the outcome definition was changed, suggesting it is an artifact of confounding, species composition, or how outcomes were measured rather than a real biological effect.

That fragility connects to one of the study’s most instructive methodological episodes. Before modeling, the team cross-checked their locked outcome file against a prespecified rule and found that 36 episodes with documented persistence of the same organism on repeat culture had been coded as successes. Correcting these records lifted the failure count from 152 to 188, or 19.5 percent of episodes. But because repeat urine cultures were obtained only when clinicians felt they were warranted — and were far more common in patients who were doing badly — the opportunity to detect persistence was unevenly distributed across the cohort. This differential verification, the authors acknowledge, could have distorted the very microbiological associations they set out to test.

The study’s statistical honesty is also worth noting. The regression model, after bootstrap correction for optimism, achieved an area under the curve of just 0.575 — barely better than a coin flip for individual prediction. The authors explicitly state the model was built to estimate associations, not to serve as a bedside prognostic tool. In an era when machine-learning models are routinely oversold, this kind of transparent self-assessment is a quiet corrective.

The findings echo a multicenter European study from 2019, in which treatment failure among hospitalized patients with complicated urinary tract infection was likewise driven mainly by markers of host vulnerability — intensive care admission, septic shock, catheter-associated infection — rather than by inappropriate initial antibiotics. Two cohorts, two continents, same pattern: the terrain matters more than the invader’s armaments.

None of this lets antimicrobial resistance off the hook. Resistant bacteria constrain which drugs can be used, how quickly effective therapy can start, and how complex definitive treatment becomes — and in a setting like Misurata, where over half of urinary isolates are multidrug-resistant, those constraints are daily realities. But the study suggests that resistance phenotype is best understood as one input into a broader clinical pathway, not a standalone verdict. For clinicians, the practical takeaway is concrete: in complicated urinary infection, look first for the blocked kidney, the uncontrolled diabetes, the early sepsis, and the drainage that has not happened. Fixing the plumbing, the data imply, may save more treatments than any new antibiotic.

Subject of Research: Clinical and microbiological determinants of treatment failure in complicated urinary tract infection caused by Enterobacterales

Article Title: Clinical and microbiological determinants of treatment failure in complicated urinary tract infection: a four-hospital cohort of enterobacterales infections in Misurata, Libya

Article References: Alwashaish, M. M., Ashour, A. O., Elwash, M. E., & Elmeheishi, F. M. (2026). Clinical and microbiological determinants of treatment failure in complicated urinary tract infection: a four-hospital cohort of enterobacterales infections in Misurata, Libya. Frontiers in Medicine, 13, Article 2002811. https://doi.org/10.3389/fmed.2026.2002811

Image Credits: AI Generated

DOI: 10.3389/fmed.2026.2002811

Keywords: complicated urinary tract infection, Enterobacterales, antimicrobial resistance, beta-lactamase, ESBL, biofilm, treatment failure, sepsis, diabetes, urinary obstruction, Libya, MALDI-TOF

Antimicrobial susceptibility testing painted a nuanced picture. Resistance to cefoxitin, a proxy for methicillin resistance, was detected in 21.7 percent of CoNS isolates and 10 percent of S. aureus isolates. Tetracycline resistance appeared in 19.2 percent of CoNS and 10 percent of S. aureus, erythromycin resistance in 16.7 percent of CoNS, and resistance to gentamicin and fluoroquinolones in roughly 10 percent of isolates. Encouragingly, the vast majority of strains remained susceptible to chloramphenicol and cotrimoxazole at around 95 percent, linezolid at approximately 97 percent, and vancomycin, the last-resort glycopeptide, at a full 100 percent.

Nineteen isolates, including two S. aureus strains, proved resistant to cefoxitin, and eight of these carried the mecA gene, the genetic determinant that confers methicillin resistance by encoding an altered penicillin-binding protein. The researchers subjected all eight mecA-positive isolates to whole-genome sequencing, revealing genome sizes ranging from 2.27 to 2.78 megabases. The methicillin-resistant S. aureus isolate, designated ERSST98, possessed the largest genome and the highest number of rRNA gene copies, features often associated with metabolic versatility and adaptability.

Comparative genomic analysis exposed a patchwork of staphylococcal cassette chromosome mec elements, the mobile genetic islands that harbor methicillin resistance. The isolates displayed various SCCmec types, reflecting independent acquisition events rather than the spread of a single clone. Beyond beta-lactam resistance, the genomes carried determinants against aminoglycosides, macrolides, and tetracyclines, alongside efflux pump systems that actively expel drugs from the cell and genes conferring tolerance to heavy metals, an intriguing link to environmental selection pressures on dairy farms.

The virulence profile of the MRSA isolate ERSST98 was particularly sobering. Its genome encoded a broad arsenal of adhesins that allow the bacterium to cling to mammary tissue, toxins capable of damaging host cells, and biofilm-associated genes that enable the formation of protective communities on teat canal surfaces and milking equipment. Biofilm formation is a well-known driver of persistent, treatment-refractory mastitis, and its genetic underpinnings in this isolate underscore the pathogenic capacity lurking in dairy herds.

Equally significant was the mobilome, the collection of mobile genetic elements shuttling genes between bacteria. The sequenced isolates harbored diverse plasmid replicon types and multiple families of insertion sequences, molecular vehicles that facilitate horizontal gene transfer. This genomic plasticity means resistance traits are not locked in place; they can move between species and strains, potentially bridging the gap between animal reservoirs and human pathogens.

The findings carry weight within a One Health framework, which recognizes that human, animal, and environmental health are intertwined. Staphylococci from milk can contaminate dairy products, colonize farm workers, and seed resistant genes into the broader microbial ecosystem. The identification of methicillin-resistant CoNS alongside MRSA in raw milk suggests that these lesser-known species may serve as gene banks from which more dangerous pathogens can draw resistance determinants.

Methodologically, the study combined conventional bacteriology with modern genomics. Isolates were phenotyped using a Sensititre microdilution system provided by the Food and Agriculture Organization, and the whole-genome sequencing dataset has been deposited in the GenBank Nucleotide Database under BioProject accession PRJNA1415993, allowing other researchers to interrogate the raw data. The work was conducted under the Indian network program on antimicrobial resistance and approved by the institutional animal ethics committee.

For dairy producers and veterinarians, the message is twofold. First, mastitis control programs should not focus solely on S. aureus, since CoNS species are clearly participating in the resistance economy of the udder. Second, prudent antimicrobial use remains essential, because every treatment course applies selection pressure that can amplify resistant clones. The near-universal susceptibility to vancomycin and linezolid offers a reassuring margin, but preserving it depends on stewardship.

As sequencing costs fall, genomic surveillance of dairy-associated staphylococci is likely to become a routine component of food safety and public health monitoring. This study demonstrates that such surveillance can reveal not just which drugs fail, but why: the specific SCCmec backbones, efflux pumps, plasmids, and virulence factors that make these milk-borne bacteria formidable. In the quiet of the milking parlor, an evolving genomic arms race is underway, and only by reading the bacterial blueprint can researchers stay ahead of it.

The ecological role of coagulase-negative staphylococci in dairy settings deserves particular attention. Species such as Staphylococcus epidermidis, Staphylococcus haemolyticus, and the recently reclassified genus Mammaliicoccus are normal inhabitants of the skin and teat canal, yet they can opportunistically cause intramammary infections, especially in high-yielding herds. Because these organisms persist in close contact with both the animal host and the farm environment, they experience continuous exposure to low levels of disinfectants, heavy metals, and antimicrobial residues. Over time, such exposure favors strains that accumulate resistance machinery, and the finding that most cefoxitin-resistant isolates in this study were CoNS rather than S. aureus fits a pattern increasingly reported from dairy farms across Asia, Africa, and Europe.

The mecA gene sits at the center of methicillin resistance, but its context matters as much as its presence. The gene is embedded within the staphylococcal cassette chromosome mec, a genomic island that varies in structural organization, cassette chromosome recombinase composition, and regulatory elements. Different SCCmec types can influence how stably resistance is maintained, how readily it is transferred, and whether the resistant strain carries additional virulence cargo. The observation of multiple SCCmec types among just eight sequenced isolates suggests that methicillin resistance emerged independently several times within these herds, likely through local acquisition of the cassette by susceptible resident strains rather than through the clonal expansion of a single introduced lineage.

Heavy metal resistance genes, which featured prominently in the sequenced genomes, illustrate a subtle but important dimension of antimicrobial resistance on farms. Copper, zinc, and other metals are used in footbaths, teat dips, feed supplements, and building materials. Genetic determinants that tolerate these metals frequently reside on the same plasmids or genomic islands as antibiotic resistance genes, so exposure to metals alone can co-select for antibiotic resistance even in the absence of drug pressure. This co-selection dynamic complicates stewardship efforts, because reducing antibiotic use, while essential, may not fully relieve selection if metal exposure remains high.

The efflux systems identified in the isolates add another layer of concern. Multidrug efflux pumps of the major facilitator superfamily can export structurally unrelated compounds, including tetracyclines, macrolides, and biocides, and their expression is often inducible by the very substances they expel. In biofilm-forming strains, efflux activity contributes to the reduced susceptibility of cells embedded in the matrix, helping explain why biofilm-associated mastitis responds poorly to standard treatment regimens even when planktonic cultures appear susceptible in laboratory testing.

From a food safety perspective, the presence of these organisms in raw milk raises questions that extend beyond the milking parlor. Staphylococci can survive in biofilms on milking equipment, contaminate cheese and other products made from unpasteurized milk, and produce heat-stable enterotoxins under favorable growth conditions. Although pasteurization eliminates vegetative cells, the enterotoxins themselves can persist, and the enterotoxin gene repertoire carried by strains such as ERSST98 underscores the value of preventing bacterial growth in the first place rather than relying on downstream control measures.

The economic dimension of mastitis compounds these biological concerns. Mastitis remains one of the costliest diseases of dairy cattle worldwide, driving losses through reduced milk yield, discarded milk, treatment expenses, culling, and labor. In India, where smallholder and mixed farming systems dominate milk production, subclinical infections often go undetected, allowing resistant strains to circulate silently within herds and to shed continuously into the bulk milk supply. Genomic surveillance offers a way to detect such circulation early, identifying emerging resistance determinants before they become entrenched.

The public deposit of the sequencing data under a public BioProject accession also reflects a broader shift in how antimicrobial resistance research operates. Openly shared genomes allow investigators in other regions to compare isolates, track the movement of specific lineages across borders, and build cumulative databases that reveal trends no single study could detect. For a pathogen group as genomically fluid as staphylococci, such comparative resources are indispensable for distinguishing local evolutionary events from genuine inter-regional transmission.

Finally, the study’s findings resonate with ongoing global efforts to contain antimicrobial resistance in food-producing animals. International guidance increasingly emphasizes integrated surveillance across human, animal, and environmental sectors, and dairy-associated staphylococci sit squarely at that intersection. The combination of methicillin resistance, multidrug determinants, heavy metal tolerance, and biofilm capacity in milk-borne isolates demonstrates that farms are not merely passive reservoirs but active arenas of resistance evolution. Sustained genomic monitoring, coupled with improved hygiene, judicious antimicrobial use, and attention to co-selective pressures such as metals, offers the most realistic path toward keeping these organisms from bridging the gap between animal husbandry and human clinical medicine.

Subject of Research: Genomic diversity and antimicrobial resistance determinants of staphylococci isolated from cow and buffalo milk

Article Title: Genomic diversity and resistance determinants of staphylococci from cow and buffalo milk

Article References: Banerjee, J., Karim, S. M., Sharma, D., Choudhury, B., Biswas, S., Samanta, I., Nanda, P. K., Biswas, T. K., Kumar, M. S., Dandapat, P., Sen, A., & Bandyopadhyay, S. (2026). Genomic diversity and resistance determinants of staphylococci from cow and buffalo milk. Molecular Biology Reports, 53(1), Article 1536. https://doi.org/10.1007/s11033-026-12729-3

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12729-3

Keywords: MRSA, coagulase-negative staphylococci, mastitis, dairy milk, antimicrobial resistance, whole genome sequencing, SCCmec, mecA, virulence genes, One Health, plasmids, biofilm

The stakes are higher than they might first appear. Across Europe, the ecological health of rivers and lakes is formally assessed under the Water Framework Directive using biological indicators, and in the United Kingdom one of the key tools is the Trophic Diatom Index, or TDI. Diatoms, the single-celled algae with ornate silica cell walls that dominate the phytobenthos of freshwaters, are scraped from biofilm-covered stones, identified either under the light microscope or, increasingly, through high-throughput DNA sequencing. The composition of the diatom assemblage reflects nutrient enrichment and other pressures, and the resulting Ecological Quality Ratio feeds directly into official classifications of whether a river is in good status or failing. But biofilms are far more than diatoms. They are slimy microbial cities, embedding bacteria, fungi, diverse algae, and protozoa within a protective extracellular matrix, and together these organisms drive primary productivity, decomposition, biogeochemical cycling, and pollutant degradation. Scientists have long argued that this broader microbial diversity could yield new diagnostic indicators of human impacts, and recent advances in machine learning and network analysis have made the search for such microbial metrics technically feasible.

The bottleneck has always been data. To identify reliable microbial features that can be upscaled into bioindicators of ecosystem function, researchers need thousands of samples spanning wide geographic areas and meaningful timescales. Generating such datasets from scratch is prohibitively expensive, requiring extensive field campaigns and laboratory analysis. This is precisely where the archive becomes revolutionary. Every year, the Environment Agency of England collects biofilm samples from rivers across the country as part of routine diatom monitoring, and each sample is preserved in an RNAlater-based nucleic acid preservative, a solution of 3.5 M ammonium sulphate, 17 mM sodium citrate, and 13 mM EDTA, before being frozen at -20 °C. A previous study by Baricevic and colleagues in 2022 had shown that such preserved samples remained stable for twelve months, with no significant impact on DNA quality, yield, or the composition of the diatom assemblages. But nobody knew whether the samples would survive intact over multiple years, and the answer to that question determined whether the archive could be treated as a genuine scientific resource or merely as regulatory paperwork.

To find out, the research team selected 64 frozen biofilm samples that had originally been collected and analysed in 2019 and 2020 as part of routine monitoring, chosen to cover a broad geographic spread across England and to have passed rigorous quality control with more than 50,000 reads in the original sequencing run. In December 2022, after two or three years in the freezer, the samples were thawed and reanalysed, and crucially the reanalysis was performed twice on separate sub-samples from each archived specimen. This duplication was the study’s methodological masterstroke, because it allowed the researchers to disentangle any genuine changes caused by storage from the inevitable stochastic noise introduced by sub-sampling, PCR amplification, and sequencing. In total, 192 samples were sequenced across the three sub-sample groups, designated OG for the original analysis and RA and RB for the post-storage replicates, generating 12.9 million quality-controlled reads and revealing 5,138 unique amplicon sequence variants.

The laboratory workflow followed the standard protocol established for routine monitoring. Biofilm-covered stones had been scrubbed with a clean toothbrush in deionised or tap water, the suspension mixed with preservative and couriered overnight to the laboratory, and the samples stored as concentrated pellets at -20 °C. For the reanalysis, samples were thawed, centrifuged at 3000 × g to reform a concentrated pellet, and DNA was extracted using a Qiagen blood tissue kit with an extended overnight lysis step at 56 °C. The target region was the rbcL chloroplast gene, amplified with primers rbcL-646F and rbcL-998R, which capture diatoms but also amplify other non-diatom phytobenthos. The resulting amplicon libraries were purified with SPRI beads, tagged with Illumina Nextera XT unique dual-indexed adapters, normalised, pooled, and sequenced on an Illumina MiSeq. Bioinformatic processing in QIIME2 employed cutadapt for primer removal, DADA2 for denoising and chimera removal, and a multinomial naïve Bayes classifier trained on the diat.barcode reference database for taxonomic assignment, with no filtering so that both diatom and non-target phytobenthic sequences were retained throughout the analysis.

The statistical verdict was unambiguous. At the amplicon sequence variant level, differences in diatom assemblages were overwhelmingly explained by differences between sample sites, accounting for 38.3 per cent of the variation, while storage conditions between the original and post-storage sub-samples explained less than 1 per cent and were not statistically significant. When the researchers specifically compared two versus three years of storage, the result was equally insignificant. At the genus and species levels, no taxa were detected at significantly higher abundance after storage, and the vast majority of genera, 84.0 per cent, were found in all replicate groups. The few genera and species that appeared unevenly between replicates were detected at very low levels, typically fewer than 1,000 reads across only one to three samples, and almost all belonged to genera that were more widely detected across the dataset. Only two diatom species, Surirella solea and Placoneis constans, were uniquely detected in post-storage replicates without their genus being more widely found, and even these appeared at negligible abundance. Curiously, the non-target species Quercus robur, the English oak tree, was detected in three post-storage replicates only, almost certainly the result of trace contamination or incidental amplification rather than any meaningful biological signal.

Perhaps most importantly for regulators, the ecological status metrics derived from the DNA were remarkably consistent. The mean difference in TDI values before and after storage was just 3.18, and Pearson’s correlation coefficients between the three replicate groups ranged from 0.892 to 0.980, all highly significant. When ecological status classes were assigned, 75.8 per cent of samples received the same classification across all replicates, and 79.0 per cent were either identical or differed by only one class. In pairwise comparisons, the original and first post-storage replicate agreed on the same class for 90.4 per cent of samples. Only four samples stood out as clear outliers, with differences greater than one class depending on which replicates were compared. In one of these, the post-storage replicate contained a much larger proportion of the diatom Amphora pediculus, at 47.1 per cent, than the original and first replicate, at 22.2 and 17.5 per cent respectively. But because no species were differentially abundant between replicate groups across the dataset as a whole, the researchers concluded that these outlier differences were not caused by fundamental changes from storage, but rather by the same sub-sampling and PCR variation that plagues any routine monitoring data.

This interpretation places the study in a broader scientific context. The magnitude of the insignificant differences observed between original and post-storage analyses was similar to that reported in previous work when comparing differences between different analysts and different sequencing instruments, suggesting that the noise inherent in the analytical pipeline itself is comparable to or greater than any effect of multi-year storage. Comparable findings have emerged from studies of other microbial sample types. Researchers examining bacterial communities in faecal samples stored for five years in preservative at -80 °C found them comparable to reference samples, and multiple shorter-term studies have reported similar stability. However, the literature is not entirely uniform, as one study found that RNAlater significantly affected bacterial communities compared to liquid nitrogen freezing at one of two sites tested, while finding no significant differences for fungal communities. The authors of the current study caution that extrapolating their results to the wider microbial community requires care, because research on the stability of bacterial communities by 16S metabarcoding is contradictory and difficult to compare directly, and little research has been conducted on the impact of storage conditions on fungi or protists within biofilms.

The practical implications extend well beyond diatoms. The study further evidences RNAlater-based preservation of freshwater biofilms as a viable alternative to ethanol, one of the standard recommended methods under European standardisation guidelines. For logistical, health, and safety reasons, the Environment Agency has restrictions on the use of ethanol, and therefore sought alternatives for the sampling and storage of biofilm samples. The confirmation that these preserved samples remain stable for up to three years means that regulators can now maximise the value of their historic raw biofilm samples, reusing them for purposes far beyond their original intent, including monitoring other non-microbial taxonomic groups and exploring the responses of broader microbial communities to environmental change. What was once a freezer full of completed regulatory assessments has been recast as a living archive, ready to yield the large, cost-effective datasets that will underpin the next generation of microbial metrics for freshwater biomonitoring, and with them, a far richer understanding of how river ecosystems respond to the mounting pressures of a changing world.

Subject of Research: Environmental DNA

Article Title: Influence of storage time on the stability of diatom assemblages using DNA from riverine biofilm samples

Article References: Warren, J., Butler, S., Evens, N., Hunt, L., Kelly, M., Newbold, L., Read, D. S., Taylor, J. D., & Walsh, K. (2024). Influence of storage time on the stability of diatom assemblages using DNA from riverine biofilm samples. Metabarcoding and Metagenomics, 8, Article e129227. https://doi.org/10.3897/mbmg.8.129227

Image Credits: AI Generated

DOI: 10.3897/mbmg.8.129227

Keywords: environmental DNA, diatoms, biofilm, biomonitoring, metabarcoding, river health, Influence, storage, time, stability, diatom, assemblages

The urgency behind the work is hard to overstate. According to the Global Burden of Disease study, drug-resistant bacterial infections were associated with 4.71 million deaths in 2021, including 1.14 million deaths directly attributable to antimicrobial resistance. Projections suggest that by 2050, annual AMR-associated deaths could exceed 8 million. A. baumannii sits at the top of the danger list: the World Health Organization classifies carbapenem-resistant A. baumannii (CRAB) as a critical priority pathogen, and the U.S. Centers for Disease Control and Prevention labels it an urgent threat. The bacterium readily acquires resistance genes, forms stubborn biofilms on medical devices, and has narrowed the therapeutic arsenal to a handful of toxic last-resort drugs.

CIT8 is a derivative of citropin 1.1, a naturally occurring alpha-helical antimicrobial peptide from an Australian tree frog. In an earlier study, the team used a machine learning-guided strategy that mined a database of more than 14,000 experimentally characterized antimicrobial peptides to identify a physicochemically distinct cluster dominated by high hydrophobicity, helicity, and an extended hydrophobic surface. Guided by that analysis, they introduced four amino acid substitutions into a truncated citropin fragment, producing CIT8 with the sequence GLFKVIKKLLKVI. The changes raised the peptide’s net positive charge and hydrophobicity, and the resulting molecule proved highly active against methicillin-resistant Staphylococcus aureus. What remained unknown was how broad its spectrum might be.

The new experiments answered that question decisively. Against a panel of 16 A. baumannii strains, including 14 clinical isolates from the FDA-CDC Antimicrobial Resistance Isolate Bank, CIT8 maintained a minimum inhibitory concentration of 4 micrograms per milliliter against 15 of the 16 strains, including multiple carbapenem-resistant isolates for which meropenem was essentially inactive. Its all-D enantiomer, CIT8-D, performed nearly as well. Time-kill assays revealed just how fast the peptide works: at 20 micrograms per milliliter, five times the MIC, CIT8 drove an initial population of roughly 5 x 10^7 colony-forming units per milliliter of exponential-phase bacteria below the limit of detection within 15 minutes. Polymyxin B, the clinical benchmark membrane-active antibiotic, needed 30 to 120 minutes to achieve the same result, while meropenem alone failed to reduce bacterial counts at all during the four-hour experiment.

The mechanism behind this speed is classic antimicrobial peptide biology. Using the membrane potential-sensitive dye DiSC3(5), the researchers observed rapid, dose-dependent depolarization of the bacterial membrane, with effects visible even at sub-inhibitory concentrations. Sytox Green uptake confirmed that the membrane became permeable to molecules that normally cannot cross it, and a luciferase-based assay showed leakage of intracellular ATP within an hour of exposure. Scanning electron microscopy revealed roughened, indented cell surfaces and extracellular debris in treated bacteria. Together, the data point to a membrane-targeting mode of action in which the cationic peptide binds the negatively charged bacterial surface, accumulates at the membrane interface, and catastrophically disrupts membrane integrity.

Molecular dynamics simulations added atomic-level detail. In two independent one-microsecond simulations using a model membrane of POPE and POPG lipids in a 3:1 ratio, CIT8 bound rapidly to the membrane surface and stayed there, localized in the headgroup region rather than penetrating the hydrophobic core. Potential of mean force calculations confirmed that migration from the membrane interface into the bilayer interior is energetically unfavorable, with a free energy barrier of roughly 28 kilocalories per mole. Crucially, CIT8 held a more stable alpha-helical structure than its weak parent peptide CIT1, retaining a continuous helical core from residue 4 to residue 10. The simulations also showed that CIT8 made substantially more contact with the anionic POPG lipid, particularly through the lysine substitution at position 4, which replaced a negatively charged aspartic acid.

Biofilms, the slimy bacterial communities that make A. baumannii infections so persistent, were another target. When added during biofilm formation, CIT8 reduced biofilm cell viability by more than 95 percent at concentrations of 16 micrograms per milliliter or higher, while CIT8-D achieved the same effect at 4 to 8 micrograms per milliliter. Against established 24-hour biofilms, CIT8 halved biofilm-associated cell viability at roughly 23 micrograms per milliliter in both a reference strain and a CRAB isolate, whereas CIT8-D was roughly three times more potent, achieving the same reduction at 6.6 to 10.8 micrograms per milliliter. Fluorescence microscopy using live-dead staining confirmed that CIT8-D-treated biofilms were almost entirely dead, while meropenem-treated biofilms remained mostly viable. The authors suggest that the superior antibiofilm performance of the D-enantiomer may reflect its resistance to proteolytic degradation, which preserves activity during prolonged exposure.

Safety margins matter as much as potency, and here the results were encouraging. CIT8 showed no detectable effect on the viability of human keratinocyte HaCaT cells or human kidney cortex HKC-8 cells even at 128 micrograms per milliliter, yielding a therapeutic index greater than 32 in both cell lines. CIT8-D was more cytotoxic, with median lethal concentrations of 64.6 and 74.1 micrograms per milliliter in the two cell lines and therapeutic indices of 16.2 and 18.5, but it still retained considerable selectivity for bacterial over mammalian membranes. The peptide’s activity did weaken in the presence of divalent cations such as calcium and magnesium, which stabilize the Gram-negative outer membrane by bridging adjacent lipopolysaccharide molecules, and in the presence of human serum, a reminder that physiological conditions will test any membrane-active candidate.

Perhaps the most clinically intriguing finding involves combination therapy. Standard checkerboard assays detected no synergy between CIT8 and conventional antibiotics, but time-kill assays told a different story. When 4 micrograms per milliliter of CIT8 was combined with 40 micrograms per milliliter of meropenem, viable counts of the carbapenem-resistant isolate AR33 dropped by roughly 4 log10 units relative to the starting inoculum after four hours, an additional 2.7 log10 reduction compared with CIT8 alone. Similar bactericidal synergy, meeting the prespecified threshold of at least a 2 log10 improvement over the most active single agent, was reproduced in two other CRAB isolates. Interestingly, ATP leakage assays showed no additional membrane damage in the combination groups, suggesting the interaction with meropenem is not simply a matter of enhanced permeabilization and may involve the antibiotic gaining better access to its periplasmic targets once the membrane is compromised.

The authors are careful to frame CIT8 as a scaffold rather than a finished drug. Proteolytic stability, pharmacokinetics, resistance potential, and in vivo efficacy all remain to be established, and the reduced activity in serum and in the presence of divalent cations underscores the need for testing in more complex biological matrices. Still, the study makes a compelling case that machine learning-guided sequence optimization, originally aimed at MRSA, can produce molecules with unexpected breadth against Gram-negative priority pathogens. As generative and predictive models for antimicrobial peptide design continue to mature, CIT8 offers a concrete example of how a few rationally chosen amino acid substitutions, validated by rigorous experiments, can transform a modest frog-skin fragment into a candidate worth serious preclinical attention in the fight against one of medicine’s most dangerous bacteria.

Subject of Research: Experimental characterization of the machine learning-optimized antimicrobial peptide CIT8 against carbapenem-resistant Acinetobacter baumannii

Article Title: CIT8, a machine learning-optimized antimicrobial peptide, exhibits potent activity against carbapenem-resistant Acinetobacter baumannii

Article References: Dellis, C., Mishra, B., Zhang, L., Basu, A., Felix, L. O., Shehadeh, F., Ganesan, N., Kolocouris, A., & Mylonakis, E. (2026). CIT8, a machine learning-optimized antimicrobial peptide, exhibits potent activity against carbapenem-resistant Acinetobacter baumannii. Frontiers in Microbiology, 17, Article 1967486. https://doi.org/10.3389/fmicb.2026.1967486

Image Credits: AI Generated

DOI: 10.3389/fmicb.2026.1967486

Keywords: antimicrobial peptides, Acinetobacter baumannii, carbapenem resistance, machine learning, antimicrobial resistance, membrane disruption, biofilm, meropenem synergy, citropin, molecular dynamics, therapeutic index, CRAB

Bernier Cave is the type locality for A. stygobita, which was described in 2011 as the world’s first known cave brittle star. The species is endemic to Bernier Cave and the nearby Lighthouse Cave, though it is significantly more abundant in the former. Finding these animals is challenging because their small disks, measuring only 3 to 4 millimeters in diameter, are filled with brown detritus that camouflages them against the cave walls. Laboratory experiments have shown that A. stygobita does not accept standard brittle star food but readily consumes the diatom-rich detritus collected from the cave. This specialized diet appears to be the primary reason the population remains stable in this unique habitat.

The cave environment plays a crucial role in supporting this food web. Bernier Cave features a large ceiling entrance that allows both substantial amounts of light and organic detritus to reach the aquatic ecosystem. The water in the cave is brackish, with salinities ranging from 14 to 28 parts per thousand. Tidal fluctuations are relatively slight compared to the surrounding ocean, resulting in slow water movement that allows sizeable accumulations of detritus to settle. A distinctive brown tide line visible on the cave walls is composed largely of C. neofastuosus and other microbes, indicating the prolific growth of this diatom in the entrance room where light is most available.

Campylodiscus neofastuosus, formerly known as Surirella fastuosa, is a large diatom that thrives in brackish water. In the detritus of Bernier Cave, it forms the backbone of the microbial community. While smaller diatom species such as Amphora, Achnanthes, and Orthoseira are more numerous in terms of individual count, C. neofastuosus dominates the biomass due to its large size. The detritus also contains a diverse array of other organisms, including filamentous Chlorophyta, nematodes, ostracods, harpacticoid copepods, ciliates, dinoflagellates, foraminifera, and various bacteria. White bacterial mats, primarily consisting of filamentous sulfur bacteria like Beggiatoa, are also present and are closely associated with the diatom-rich detritus.

One of the most fascinating aspects of C. neofastuosus is its morphological adaptation to the low-light conditions of the cave. The diatom possesses a distinctive cell wall, or frustule, that is concave and slightly heteropolar, resembling a plano-concave lens. This shape is ideal for projecting and focusing light. The frustule acts as an optical device, concentrating the limited available light onto the lens-shaped central area of the cell. Additionally, the diatom has a canal raphe that enhances its motility, allowing it to position itself at the optimal angle for light capture. This structural adaptation is critical for maximizing photosynthetic efficiency in an environment where light is scarce.

The chloroplasts of C. neofastuosus also exhibit remarkable plasticity in response to light levels. In total darkness, the chloroplasts fill almost the entire cell, appearing dark brown due to high concentrations of fucoxanthin. Fucoxanthin is a pigment that efficiently harvests light and transfers excitation energy to chlorophyll a. Under low light conditions, the chloroplasts become lobed and follow the costae, or ribs, of the cell wall, concentrating pigment in the lens-shaped interior. In brighter light, the chloroplasts become more compact and rounded around the nucleus, likely to protect DNA from ultraviolet radiation. This dynamic shape-shifting allows the diatom to optimize its light capture strategy based on environmental conditions.

Beyond its role in photosynthesis, C. neofastuosus produces extracellular polymeric substances, or EPS, which are essential for the formation of the detritus biofilm. These EPS are rich in polysaccharides, monosaccharides, and proteins, and they contain diatom oils including Omega-3 fatty acids. The EPS acts as a sticky glue, binding together various particles and microorganisms to form a fabric-like consistency. This structure is similar to marine snow found in deep-sea environments, which transports nutrients from surface blooms to the abyss. In the cave, this biofilm provides a manageable food source for the brittle star, allowing it to pull the detritus into its mouth with ease.

The nutritional value of the detritus is further enhanced by the symbiotic relationships within the biofilm. The EPS layer, known as the phycosphere, attracts heterotrophic bacteria that supply the diatoms with essential nutrients and cofactors, such as vitamin B12, which diatoms cannot produce themselves. This exchange creates a rich, energy-dense food web that supports not only the brittle star but also a diverse population of detritivores, including nematodes, ostracods, and copepods. The presence of C. neofastuosus makes the detritus in Bernier Cave distinct from that found in other caves, providing a high-quality food source that sustains the endemic population of A. stygobita.

This research underscores the importance of understanding the complex interactions between microorganisms and their environments in subterranean ecosystems. The ability of C. neofastuosus to adapt its morphology and chloroplast structure to low light conditions, combined with its production of nutrient-rich EPS, creates a unique niche that supports rare species. As cave ecosystems continue to face threats from climate change and human activity, preserving these delicate microbial communities is crucial for the survival of endemic species like the cave brittle star. The findings from Bernier Cave offer valuable insights into the resilience of life in extreme environments and the intricate mechanisms that allow organisms to thrive in the absence of abundant light.

Subject of Research: Diatom biofilm ecology and cave brittle star nutrition

Article Title: A biofilm micro-community dominated by the diatom Campylodiscus neofastuosus ( Surirellales ) binds detritus used as food source for rare brittle stars endemic to two Bahamian caves

Article References: Steinitz-Kannan, M., Carpenter, J. H., & Nienaber, M. A. (2025). A biofilm micro-community dominated by the diatom Campylodiscus neofastuosus (Surirellales) binds detritus used as food source for rare brittle stars endemic to two Bahamian caves. Subterranean Biology, 51, 197-212. https://doi.org/10.3897/subtbiol.51.141192

Image Credits: AI Generated

DOI: 10.3897/subtbiol.51.141192

Keywords: diatoms, cave ecology, brittle stars, biofilm, photosynthesis, Bahamas, microbiology, subterranean biology, Campylodiscus neofastuosus, Amphicutis stygobita, micro-community, dominated

The clinical burden underlying this research direction is substantial. Osteomyelitis, the infection of bone marrow and surrounding bone tissue addressed in the review, is driven most often by Gram-positive staphylococci, with Staphylococcus aureus alone implicated in roughly 44% to 75% of cases and particularly dominant in chronic presentations. Once established, these infections resist conventional treatment not simply because the bacteria themselves are hardy, but because they organize into biofilms—structured communities that adhere to implant surfaces, necrotic bone fragments, and other hospitable niches. Within these communities, bacteria are shielded from both innate and adaptive immune responses and display markedly reduced susceptibility to antimicrobial drugs. The result is a vicious cycle in which surgical debridement and prolonged antibiotic courses frequently fail to eradicate the infection, leaving many patients to progress to chronic disease marked by inflammation-driven bone destruction, heightened osteoclast activity, and secondary osteonecrosis.

The piezoelectric principle at the heart of the proposed strategy rests on a deceptively simple physical property. Materials with non-centrosymmetric crystal lattices—meaning their internal structure lacks a center of symmetry—develop separated positive and negative charge centers when mechanically deformed. This deformation generates electric dipoles and, on the material surface, localized bound charges. The phenomenon runs in both directions: the direct piezoelectric effect converts applied mechanical force into electrical charge, while the inverse effect converts an applied electric field into mechanical deformation. For biomedical purposes, the direct effect is the more relevant one, since it allows the body’s own mechanical environment—walking, loading, ultrasound applied from outside, even subtle internal tissue movements—to be harvested as a source of localized electrical stimulation without any external power supply implanted at the site.

What makes this particularly attractive for infected bone is the multiplicity of antibacterial mechanisms that can flow from that single physical event. When a piezoelectric surface is mechanically stimulated, the resulting charge separation can, in catalytically active systems, drive redox reactions that generate reactive oxygen species. These highly reactive molecules damage bacterial membranes, interfere with intracellular redox balance and respiratory processes, and attack the extracellular polymeric matrix that gives biofilms their structural integrity. Importantly, the review emphasizes that reactive oxygen species are not the whole story. Electrical perturbation at the material surface, direct mechanical disruption of biofilm architecture, interfacial electron transfer, and the release of metal ions can each contribute to bacterial killing and biofilm dismantling. This mechanistic plurality matters clinically, because a therapy that attacks bacteria through several parallel pathways is inherently less vulnerable to the resistance mechanisms that defeat single-target antibiotics.

The review’s authors argue that the field has tended to organize itself around material classifications, antibacterial mechanisms, or application categories, and that this taxonomy has obscured something clinically essential: bone infection is not a static problem but a dynamic pathological sequence. Persistent biofilms, dysregulated antimicrobial immunity, excessive or unresolved inflammation, and impaired angiogenesis and osteogenesis are not independent events. They are interconnected processes that unfold in a characteristic order as infection is controlled and repair proceeds. A material that aggressively generates reactive oxygen species may be ideal in the first days after debridement, when bacterial load and biofilm burden are highest, yet counterproductive weeks later, when the priority shifts to protecting nascent blood vessels and differentiating osteoblasts from oxidative damage.

To resolve this tension, the authors propose a stage-adaptive therapeutic framework. In the early infection-control phase, the priorities are biofilm disruption, bacterial eradication, and activation of antimicrobial immune functions. Piezoelectrically generated electrical signals and reactive oxygen species serve these goals directly, while the same stimuli can polarize immune cells toward a microbicidal phenotype that complements the materials’ direct antibacterial action. Once the infectious burden has been sufficiently reduced, the therapeutic emphasis must pivot: oxidative stress must now be contained, persistent inflammation resolved, and the immune microenvironment remodeled toward a pro-reparative state that supports angiogenesis—the sprouting of new blood vessels that supply regenerating tissue—followed by osteogenesis, the deposition of new bone matrix.

This reframing has practical consequences for material design. Rather than seeking a single material that maximizes every desirable property simultaneously, the framework suggests that next-generation implants might be engineered to modulate their own behavior over time, for example by tuning piezoelectric output, incorporating catalytic components whose activity is triggered by the local microenvironment, or layering coatings that release pro-regenerative signals only after the acute phase has passed. The review also situates piezoelectric materials within a broader lineage of biomedical applications; these substances already serve as nanogenerators in soft tissue repair and underpin technologies from medical ultrasound transducers to aerospace actuators and radio-frequency filters in consumer electronics, reflecting decades of industrial maturation that could accelerate clinical translation.

The immune dimension of the framework deserves particular attention, because it connects the antibacterial and regenerative phases into a coherent narrative. The review synthesizes evidence that piezoelectric stimulation can modulate the infection-associated immune microenvironment, steering the inflammatory response in ways that support both bacterial clearance and subsequent repair. This is a subtle balancing act. The same inflammatory programs that mobilize bactericidal activity early in infection can, if left unresolved, drive the bone destruction and fibrosis that characterize chronic osteomyelitis. A material platform that first amplifies antimicrobial immunity and then facilitates its resolution—without requiring drug interventions at each transition—would address one of the most persistent failures of current therapy, in which dysregulated host responses perpetuate disease even after bacteria have been substantially cleared.

The authors are candid about the obstacles that remain between this framework and routine clinical use. Material design optimization is an ongoing challenge: piezoelectric coefficients, biocompatibility, degradation behavior, and mechanical properties must be balanced within a single implantable system, and the optimal parameters likely differ between the infection-control and repair phases. Mechanistic understanding also remains incomplete. While the individual pathways—piezocatalytic reactive oxygen generation, electrical stimulation of cells, immune modulation—have each been demonstrated, their relative contributions in vivo, their interactions with one another, and their dependence on the local mechanical loading environment are not yet fully mapped. Clinical translation faces the additional hurdle that most supporting evidence comes from in vitro and preclinical models, which rarely reproduce the complexity of human osteomyelitis with its mixed bacterial populations, devitalized bone, and compromised vascularity.

Nevertheless, the conceptual contribution of the review lies in its insistence that therapeutic functions be evaluated against the pathophysiological timeline of the disease rather than in isolation. By integrating antibacterial action, immunomodulation, and regeneration into a single stage-adaptive sequence, it offers researchers a design logic: identify which phase of the disease a given material property serves, and engineer materials whose properties evolve in step with the patient’s needs. If that logic can be validated experimentally and carried through to clinical devices, piezoelectric biomaterials could shift the treatment of infected bone from a reactive cycle of debridement and antibiotics toward an active, self-regulating partnership between implant and host tissue—one in which the mechanical energy of everyday movement becomes a therapeutic resource deployed precisely when and where the healing process requires it.

Subject of Research: Piezoelectric biomaterials for treating bone infection through bacterial eradication, immune modulation, and bone regeneration

Article Title: Immunomodulation and biofilm disruption of piezoelectric materials in bone infection

Article References: Wang, Z., Zheng, K., Tang, Y., Zhang, Z., Zhong, Z., Wang, D., Chen, Z., Wang, Y., Chen, Z., Feng, P., Huang, W., Liu, M., Hao, Y., Yu, F., Wang, G., Yi, M., & Deng, X. (2026). Immunomodulation and biofilm disruption of piezoelectric materials in bone infection. Frontiers in Cell and Developmental Biology, 14, Article 1976300. https://doi.org/10.3389/fcell.2026.1976300

Image Credits: AI Generated

DOI: 10.3389/fcell.2026.1976300

Keywords: piezoelectric materials, bone infection, biofilm, osteomyelitis, reactive oxygen species, immunomodulation, bone regeneration, antibacterial biomaterials, disruption, piezoelectric, materials, bone

The therapeutic arsenal against this yeast is eroding. Overuse and misuse of antifungal drugs have fueled the emergence of resistant C. albicans strains, and studies have documented resistance to widely used agents such as fluconazole and itraconazole, contributing to chronic and recurrent infections. Non-albicans Candida species are increasingly recognized as additional treatment challenges. This growing resistance has pushed researchers toward alternative approaches, including postbiotic metabolites, yet studies evaluating the direct effects of postbiotic mediators on fungal biofilms have remained limited.

Probiotics, live microorganisms that can suppress the growth and colonization of C. albicans, have attracted attention for managing oral candidiasis. They produce antifungal compounds such as lactic acid and bacteriocins, and may offer benefits including reduced adverse effects compared with antifungal medications and immunomodulatory effects. But live probiotics carry drawbacks: delayed effects, variable efficacy among individuals, and an increased risk of infection in immunocompromised patients. Postbiotics sidestep these concerns. Defined as non-viable microbial preparations or their components that retain bioactive properties, postbiotic mediators are sterile, cell-free, filter-sterilized preparations containing bioactive metabolites produced by probiotic metabolic activity. Because they avoid administration of viable microorganisms, they may offer practical advantages in storage and formulation, making them particularly interesting for populations in whom live bacteria may be undesirable, although the safety and stability of each preparation require direct product-specific evaluation.

A new study published in MicrobiologyOpen investigated the antifungal effects of postbiotic mediators derived from two of the most extensively studied probiotic strains, Lactobacillus rhamnosus GG (LGG) and Lactobacillus reuteri (LR). Both strains are known for robust growth, adhesion, pathogen antagonism, and production of antimicrobial substances. The researchers assessed the mediators’ minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) against C. albicans ATCC 10231 following Clinical and Laboratory Standards Institute M27-A3 broth microdilution guidelines, then examined their ability to destroy mature biofilms and suppress fungal metabolic activity.

The methods were rigorous. The lactobacilli were cultured in MRS broth for 48 hours, after which cultures were centrifuged and supernatants filtered through 0.22 micrometer membranes to yield sterile cell-free preparations. The pH of each preparation was adjusted to physiological values of 7.2 to 7.4 using sodium hydroxide, a step with important consequences, since organic acids such as lactic and acetic acid exert their primary antifungal effects in their protonated, acidic form. For susceptibility testing, yeast suspensions were standardized spectrophotometrically and diluted in RPMI 1640 medium buffered with MOPS. For biofilm assays, a higher inoculum of 1.5 × 10⁶ CFU/mL was used to ensure confluent and reproducible biofilm formation within the incubation period.

The results were striking. The MIC for both LGG-derived and LR-derived postbiotic mediators was 25 percent (v/v), and no fungal growth appeared on agar at concentrations above this level, confirming the MFC value. Because the MFC equaled the MIC for both preparations, the mediators demonstrated fungicidal activity against planktonic cells. In the biofilm destruction assay, colony-forming unit enumeration showed that both mediators yielded lower viable counts than the untreated control, but the reduction was statistically significant only for the LGG group (p = 0.0038) and not for the LR group (p = 0.1537). The authors note that the absolute reduction for LGG, while significant, was relatively modest, approximately a 17.5 percent decrease relative to control, or about 0.08 log₁₀.

Scanning electron microscopy painted a vivid picture of what the treatments did to biofilm architecture. Biofilms formed on tooth slabs, fixed with glutaraldehyde, dehydrated through ascending ethanol concentrations, and coated with palladium-gold revealed reduced microbial density and fewer microcolonies on treated surfaces, with LGG-derived mediators producing the more pronounced antibiofilm effect. The XTT reduction assay, which measures metabolic activity by detecting absorbance of reduced tetrazolium compound at 490 nm, showed that both mediators significantly suppressed biofilm metabolic activity at half the MIC: mean absorbance fell from 1.78 ± 0.09 in the control to 0.96 ± 0.06 for LGG (p = 0.0009) and 1.12 ± 0.08 for LR (p = 0.0015). This indicates that the mediators exerted biologically relevant effects on biofilm physiology even though they did not achieve rapid, high-level killing of biofilm-embedded cells within the 24-hour exposure window.

The disparity between the two strains, despite comparable MIC and MFC values, may reflect strain-specific differences in metabolite composition and biofilm-targeted mechanisms. While MIC and MFC assays primarily assess fungicidal activity against planktonic cells, LGG mediators may contain metabolites such as biosurfactants, proteases, or bacteriocins that destabilize biofilm architecture by affecting extracellular matrices or hyphal formation, a critical virulence trait of C. albicans. Prior work offers clues: LGG’s major secretory peptidoglycan hydrolase Msp1 has been shown to contribute to chitin degradation in C. albicans hyphae, and lactic acid in LGG-derived preparations affected the glucan coating on hyphal surfaces, potentially making hyphae more accessible to Msp1 activity. LR, meanwhile, produces various organic acids including acetic, lactic, oxaloacetic, propanoic, decanoic, and benzoic acids, which may contribute to growth restriction or fungal cell deformation.

The study has important limitations that temper enthusiasm. Only one reference strain of C. albicans was evaluated, so the results cannot be assumed to represent the susceptibility of genetically diverse clinical isolates, antifungal-resistant strains, or non-albicans Candida species. The postbiotic mediators were tested as crude, chemically uncharacterized preparations, leaving the concentrations and relative contributions of organic acids, peptides, bacteriocin-like compounds, and other metabolites unknown; metabolomic approaches such as LC-MS/MS should be used to identify the active components. Mechanisms of action were not directly investigated, cytotoxicity and biocompatibility were not assessed in mammalian cell models, and all experiments were performed in vitro without reproducing salivary flow, host immune responses, or polymicrobial oral biofilms. The pH adjustment may also have reduced the activity of pH-sensitive organic acids, and no standard antifungal comparator such as fluconazole was included for direct benchmarking.

These caveats aside, the findings demonstrate that cell-free postbiotic mediators from LGG and LR suppress the metabolic activity of C. albicans biofilms, with LGG-derived preparations showing the greater antibiofilm effect and electron microscopy confirming altered biofilm architecture. As antifungal resistance continues to spread and dental caries remains a burden on public health, especially among children, postbiotics offer a compelling direction: the antimicrobial benefits of probiotic bacteria without the risks of administering live microorganisms. Before therapeutic or preventive applications are considered, future research must evaluate diverse clinical and resistant Candida isolates, chemically characterize the active metabolites, investigate hyphal transition and membrane integrity, assess cytotoxicity in oral epithelial and fibroblast models, and test efficacy in physiologically relevant in vivo conditions. The road from laboratory dish to dental clinic is long, but this study marks a meaningful step along it.

Subject of Research: Antifungal and antibiofilm activity of postbiotic mediators from Lactobacillus rhamnosus GG and Lactobacillus reuteri against Candida albicans

Article Title: Antifungal Activity Assessment of Postbiotic Mediators Derived From Lactobacillus rhamnosus GG and Lactobacillus reuteri Against Candida albicans

Article References: Amirinia, F., Banakar, M., Alaeddini, M., Etemad‐Moghadam, S., Pourhajibagher, M., & Noori, M. (2026). Antifungal Activity Assessment of Postbiotic Mediators Derived From Lactobacillus rhamnosus GG and Lactobacillus reuteri Against Candida albicans. MicrobiologyOpen, 15(5), Article e70439. https://doi.org/10.1002/mbo3.70439

Image Credits: AI Generated

DOI: 10.1002/mbo3.70439

Keywords: postbiotics, Lactobacillus rhamnosus GG, Lactobacillus reuteri, Candida albicans, biofilm, antifungal resistance, oral health, Antifungal, Activity, Assessment, Postbiotic, Mediators

The epidemiological significance of NTM diseases was not fully appreciated until the early 1950s, many decades after Robert Koch announced the discovery of Mycobacterium tuberculosis in 1882. It was not until the mid-1980s that clinicians described the non-classic, nodular-bronchiectatic form of NTM pulmonary infection, distinguishing it from the previously recognized classic, cavitary presentation. By the late 1980s, bronchiectasis itself was still regarded as an orphan disease. Since then, the field has rapidly evolved into one of the fastest-growing areas of interest in respiratory medicine, yet research on NTM infections continues to lag markedly behind that devoted to tuberculosis.

The Research Topic curated by the editorialists includes one review exploring the cause-and-effect relationship between the two conditions, a case report of infection caused by the uncommon species Mycobacterium colombiense that led to the development of bronchiectasis, and three original research articles. The first study examines the epidemiology of NTM infection and concludes that the available evidence does not support person-to-person transmission. The second analyzes differences in granuloma formation induced by M. tuberculosis and M. avium. The third describes a murine model that replicates key features of cystic fibrosis, a condition closely associated with the development of bronchiectasis.

Rubio and colleagues investigated pathogen transmission by analyzing the cluster structure of 46 M. avium complex isolates obtained from patients with bronchiectasis, using whole-genome sequencing. Bronchiectasis provides a favorable environment for mycobacterial proliferation and facilitates their expulsion from the lungs through coughing. The researchers identified two clusters, each composed of two strains from different patients, isolated more than a year apart and without any evident epidemiological link, prompting the conclusion that person-to-person transmission had not occurred. If these strains share a common ancestor, the mode of transmission remains unresolved and is likely to involve indirect routes such as fomites, an area currently under active investigation. This study also offers valuable insights into the genomic diversity of M. intracellulare and M. avium species.

Among the species most frequently isolated today are M. avium, M. intracellulare, and M. abscessus. New NTM species, however, continue to be identified in clinical settings. An interesting example is the case reported by Tan and colleagues, describing the isolation of M. colombiense, a member of the M. avium complex, from a patient with bronchiectasis. Taken together, this and other cases reported in the scientific literature suggest that bronchiectasis, initially associated primarily with M. avium infection, can develop in the context of infection by a wide range of mycobacterial species. The authors highlight the need for heightened surveillance for NTM in bronchiectasis patients. It remains uncertain whether any mycobacterial species, including those not previously associated with human disease, are capable of inducing bronchiectasis in a susceptible host. Notably, the genus Mycobacterium contains more recognized pathogenic species than any other bacterial genus.

Once in the lungs, if innate immunity fails to halt the multiplication of the bacilli, granuloma formation may ensue. Granulomas arising from NTM infection often appear on imaging as pulmonary nodules, a hallmark of the nodular-bronchiectatic form of the disease. It remains unclear which specific granuloma-associated factors drive cavity formation in tuberculosis, whereas NTM infections are more commonly associated with nodules and bronchiectasis. Doratte and colleagues address this important question by comparing tuberculous and non-tuberculous granulomas in a highly relevant primate model. Their findings show that M. tuberculosis-induced granulomas display a more aggressive and destructive profile, whereas those formed in response to M. avium exhibit signaling patterns that maintain granuloma integrity. This more stable granuloma structure may help shield the mycobacteria, promoting their persistence and the progression to chronic disease, a process in which radiologic findings may evolve from isolated nodules to established bronchiectasis.

The genetic disease most strongly associated with bronchiectasis is cystic fibrosis, caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), a chloride and bicarbonate channel that balances fluid homeostasis in epithelia. In the airways, mucus becomes dehydrated and mucociliary clearance is severely impaired, creating conditions that facilitate infection by a variety of microorganisms, including mycobacteria. A cystic fibrosis-like phenotype can be reproduced in mice by mutating the βENaC channel, which enhances sodium transport. Given that nearly all patients with cystic fibrosis eventually develop bronchiectasis, this model was used by Pearce and colleagues to examine the role of M. abscessus, an NTM species frequently isolated in this population. The results showed that the mice were able to clear the mycobacteria, leading to the conclusion that this model is not suitable for studying chronic infection. Nevertheless, a decline in lung function was observed, suggesting that the model may still be useful for investigating the early stages of bronchiectasis development, a possibility that warrants further study.

The review by Singh and colleagues may serve as a compendium of the subject matter covered in this Research Topic. The authors describe the vicious cycle that arises between NTM infection and bronchiectasis. NTM infection fuels persistent inflammation and tissue damage through cytokine release and granulomatous responses, leading to further architectural distortion of the airways and progression of bronchiectasis. In turn, the structural abnormalities and impaired mucociliary clearance characteristic of bronchiectasis increase susceptibility to NTM acquisition, perpetuating the cycle. The authors also emphasize other key aspects of the disease, such as the diagnostic challenges faced in high-burden countries, where smear microscopy cannot distinguish M. tuberculosis from NTM, making molecular methods essential, as well as the difficulty of differentiating true infection from mere colonization. According to international guidelines, confirmation of NTM pulmonary disease requires a combination of clinical symptoms, radiological abnormalities, and microbiological evidence, including at least two positive sputum cultures or one positive bronchoscopy sample. The importance of biofilm formation is also stressed, as it promotes microbial persistence and facilitates horizontal gene transfer, thereby potentially increasing antimicrobial resistance and complicating treatment.

The association between NTM infection and bronchiectasis affects an ever-growing number of patients, yet many aspects of their interplay remain poorly understood. The simultaneous rise in the incidence of both conditions is unlikely to be coincidental and may instead reflect a close and biologically meaningful connection. Moreover, the proportion of infections that progress to bronchiectasis and the proportion of pre-existing structural airway abnormalities that predispose to infection are unlikely to be equivalent. In each scenario, the therapeutic priorities would differ, creating opportunities for more tailored and personalized treatment strategies. As research continues to unravel the complex interplay between these mycobacteria and the structurally compromised lung, the editorial underscores the need for continued vigilance, improved diagnostics, and a deeper mechanistic understanding to guide future clinical practice.

Subject of Research: The relationship between non-tuberculous mycobacterial infection and bronchiectasis

Article Title: Editorial: Non-tuberculous mycobacteria and bronchiectasis

Article References: Rivero-Lezcano, O. M., López-Medrano, R., & Esteban, J. (2026). Editorial: Non-tuberculous mycobacteria and bronchiectasis. Frontiers in Tuberculosis, 4, Article 1819209. https://doi.org/10.3389/ftubr.2026.1819209

Image Credits: AI Generated

DOI: 10.3389/ftubr.2026.1819209

Keywords: non-tuberculous mycobacteria, bronchiectasis, Mycobacterium avium complex, Mycobacterium abscessus, cystic fibrosis, granuloma, whole-genome sequencing, mucociliary clearance, pulmonary infection, CFTR, biofilm, epidemiology

The research team, led by David Broderick with Arne Koefoed, Steffen Albrecht, Richard Douglas and Kristi Biswas, grew eight clinically relevant bacterial species under carefully optimised conditions and sequenced their transcriptomes across four experimental states: planktonic growth, untreated established biofilm, biofilm treated with doxycycline, and biofilm treated with Zoono GermFree24, an aqueous non-alcoholic biocidal hand sanitiser in common use. The panel spanned methicillin-susceptible and methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus epidermidis, Moraxella catarrhalis, Streptococcus pneumoniae, and two commensal taxa, Corynebacterium accolens and Dolosigranulum pigrum, which are more often reported to suppress pathogenicity than to build biofilms themselves. Doxycycline was applied at 0.27 micrograms per millilitre, a concentration chosen to reflect reported sinonasal mucus levels after oral administration, while Zoono exposure durations ranged from 20 seconds to 5 minutes depending on species, calibrated in preliminary experiments to produce measurable but non-complete reductions in viability.

Technically, the study sequenced 32 RNA samples, one for each species-condition combination, on an Illumina NovaSeq X Plus platform after library preparation with a ribosomal RNA depletion kit. Samples yielded a median of 85.1 million fragments, with an average alignment rate of 73.1 percent, indicating robust transcriptome coverage. Because no biological replication was available within species-condition combinations, the authors deliberately avoided formal differential expression testing and false-discovery-rate inference. Instead, they ranked genes within each species by the magnitude of transcriptional change and retained the top 10 percent as fold-change-prioritised candidates, an exploratory strategy designed to capture the strongest responses within each organism for downstream cross-species comparison rather than to claim statistical significance.

The cross-species comparison rested on ortholog clustering. Protein sequences predicted with Prodigal were clustered using MMseqs2 at a minimum threshold of 30 percent sequence identity and 50 percent coverage, a compromise chosen to detect related protein families across phylogenetically diverse airway bacteria despite substantial sequence divergence. Sensitivity analyses at stricter thresholds of 40 percent identity with 60 percent coverage and 50 percent identity with 70 percent coverage confirmed that the broad conclusions were not an artefact of a single clustering scheme. Functional annotation drew on Swiss-Prot and Pfam databases, with genes grouped into broad biological processes covering metabolism and energy, transport, information processing, regulation and stress, cell envelope and membrane functions, and poorly characterised other functions. Directional agreement, defined as the proportion of species sharing the majority direction of change within an ortholog cluster, was then quantified and compared against a binomial null expectation based on random assignment of transcriptional direction.

The clustering analysis identified 1,503 ortholog clusters shared across multiple species, while the fold-change approach defined 6,991 candidate genes within species. Only 875 genes were supported by both approaches, forming a high-confidence subset with evidence of both strong expression change and cross-species conservation. Gene-level conservation proved restricted: just 29 clusters were detected across all eight taxa, and under the primary clustering threshold 823 raw clusters were present in at least five species while 248 were shared across all eight. Increasing stringency to 50 percent identity and 70 percent coverage reduced these figures to 277 and 48 clusters respectively, yet 138 candidate-associated clusters remained linked to clusters present in at least five species even at the strictest threshold, showing that cross-species structure survives a range of orthology definitions.

When the researchers examined the transition from planktonic to biofilm growth, they found widespread but generally modest transcriptional changes across all species, touching metabolism and energy, transport, regulation and stress, and information processing. The relative contribution of these functional categories varied substantially between species. Corynebacterium accolens showed enrichment in transport and cell envelope-associated functions, while Moraxella catarrhalis and Staphylococcus epidermidis upregulated regulation and stress pathways. Pseudomonas aeruginosa, Dolosigranulum pigrum and Streptococcus pneumoniae displayed more distributed responses without a single dominant category, and the two S. aureus strains were similarly variable. Conserved gene-level responses were limited and primarily associated with transport and metabolic functions, with even these shared clusters showing modest effect sizes and incomplete directional agreement.

Perturbation of established biofilms told a very different story. Responses to both doxycycline and Zoono were far more heterogeneous than biofilm formation responses, with substantial variation in magnitude and direction across species. Corynebacterium accolens showed decreases in transport and membrane-associated functions, Streptococcus pneumoniae exhibited transport increases alongside stress-pathway reductions, Pseudomonas aeruginosa reduced information processing activity, and Staphylococcus epidermidis increased cell envelope and membrane responses. Doxycycline, consistent with its mechanism as a tetracycline-class antibiotic that binds the bacterial 30S ribosomal subunit and inhibits protein synthesis, was more frequently associated with changes in information processing functions, whereas Zoono induced broader but less consistently directed shifts across functional categories. Despite these differences in emphasis, both perturbations converged in their lack of cross-species conservation.

The quantitative heart of the study lies in the directional agreement analysis, and the numbers are sobering. Mean directional agreement differed only slightly from values expected under random direction assignment: 70.3 percent observed versus 67.2 percent expected for biofilm formation, 69.0 percent versus 67.2 percent for doxycycline, and 66.0 percent versus 67.2 percent for Zoono. Strongly conserved transcriptional responses were uncommon despite shared functional themes, and most ortholog clusters fell within intermediate agreement ranges. Even broadly shared orthologs, such as those associated with ATP-dependent helicases and membrane transport systems, were rarely regulated uniformly across species, reinforcing the conclusion that individual candidate genes should be read as indicators of broader functional trends rather than definitive markers of conserved responses.

The authors interpret this split through a conceptual framework of functional constraint and regulatory flexibility. Biofilm formation represents a relatively constrained adaptive state in which shared environmental pressures, including surface attachment, matrix production and nutrient limitation, narrow the range of viable adaptive states and drive partial convergence at the level of broad functional processes. Perturbation relaxes those constraints, allowing species-specific regulatory networks to resolve stress through multiple organism-specific strategies, including efflux modulation, altered membrane composition, stress-response regulator activation and metabolic state changes. This balance aligns with ecological models of microbial functional redundancy, in which similar community-level functions can be maintained despite variation in the taxa, genes or regulatory pathways responsible.

The implications for treating chronic biofilm-associated infections are significant. Because biofilm establishment involves partially conserved functional adaptation, broadly targetable pathways may exist for disrupting biofilm formation across pathogens. But the species-specific nature of stress responses suggests that broadly effective interventions against established biofilms will be harder to find, and the absence of a conserved transcriptional response to perturbation raises the possibility that sublethal or transient antimicrobial exposures, common in clinical settings, may promote heterogeneous adaptive states within microbial communities. In polymicrobial airway biofilms, where neighbouring taxa influence architecture, metabolic activity and antimicrobial susceptibility, mixed communities may contain multiple partially independent stress-response programs that resist disruption through any single conserved molecular target. The authors caution that their findings derive from monoculture biofilms without biological replication, detailed biofilm architecture validation or equivalent pharmacodynamic exposures across species, and they call for future work integrating transcriptomics with proteomic, metabolomic and phenotypic measurements, extending to defined mixed-species biofilms and ex vivo or in vivo systems, and pairing comparative transcriptomics with spatial imaging and species-resolved abundance measurements to determine whether the conserved functional responses identified here are maintained, amplified or suppressed within real polymicrobial communities.

Subject of Research: Comparative transcriptomics of biofilm formation and antimicrobial perturbation across eight airway bacterial species

Article Title: Comparative RNA-Seq reveals conserved and species-specific biofilm-associated pathways across clinically relevant airway bacteria

Article References: Broderick, D., Koefoed, A., Albrecht, S., Douglas, R., & Biswas, K. (2026). Comparative RNA-Seq reveals conserved and species-specific biofilm-associated pathways across clinically relevant airway bacteria. Frontiers in Bacteriology, 5, Article 1892414. https://doi.org/10.3389/fbrio.2026.1892414

Image Credits: AI Generated

DOI: 10.3389/fbrio.2026.1892414

Keywords: biofilm, RNA sequencing, airway pathogens, comparative transcriptomics, antimicrobial perturbation, chronic rhinosinusitis, Comparative, RNA-Seq, reveals, conserved, species-specific, biofilm-associated

The research team started from a simple but consequential observation: aging is accompanied by progressive functional decline and morphological defects in cholinergic neurons, the nerve cells that use the neurotransmitter acetylcholine and whose degeneration is a hallmark of disorders such as Alzheimer’s disease. Because the human gut harbors between 10^13 and 10^14 bacteria comprising at least a thousand different species, and because bacterial metabolites can enter the circulation and cross the blood-brain barrier, the so-called microbiota-gut-brain axis has become a major focus of research into both neuroprotection and neurological disease. Lowered biodiversity and dysbiosis of the gut microbiota have been documented in elderly people and in patients with Alzheimer’s and Parkinson’s disease, raising the question of whether specific probiotic bacteria might counteract these changes.

Biofilms were central to the investigation. These are complex three-dimensional structures of adherent, cooperative bacterial communities embedded in a secreted extracellular matrix, and growth within them helps bacteria survive hostile environments. Previous work in rodent and C. elegans models had identified biofilm proficiency as a crucial determinant of both pro- and anti-neurodegenerative actions of gut bacteria. In particular, neuroprotective effects of probiotic B. subtilis strains have been linked to biofilm formation in the gut and the release of biofilm-derived metabolic and signaling factors. Some B. subtilis strains also secrete proteolytic enzymes, including the fibrin-degrading enzyme nattokinase first isolated from the Japanese food natto, which can degrade amyloid fibrils characteristic of Alzheimer’s disease.

To find the most promising candidate, the researchers screened several B. subtilis strains in vitro for biofilm production and fibrinolytic activity. The proprietary strain B4U 50, deposited at the German Collection of Microorganisms and Cell Cultures as DSM 34350, was grown for 24 hours at 37 degrees Celsius in a simulated-colonic-environment medium in 96-well plates, after which attached biofilms were stained with crystal violet and quantified spectrophotometrically. B4U 50 developed extensive biofilms under these sessile growth conditions, clearly outperforming the widely used laboratory strain NCIB3610, which showed only modest biofilm formation, while the strains 168 and JH642 produced none. On fibrin agar plates, B4U 50 also displayed the highest fibrinolytic activity of the four strains tested, generating the largest transparent hydrolysis halos, whereas strain 168 showed no detectable fibrinolytic activity at all. The biofilm- and protease-deficient strain 168 therefore served as the control in all subsequent feeding experiments.

The experimental animal was the transgenic nematode strain LX929, in which cholinergic neurons are labeled with green fluorescent protein, allowing researchers to watch neuronal aging unfold in living animals. C. elegans offers distinct advantages for this kind of work: the worms nourish on bacteria, some ingested bacteria survive to become part of their gut flora, key longevity and stress-response pathways are evolutionarily conserved between worm and human, the nervous system contains only 302 well-characterized neurons, and the animals’ transparency and short lifespan permit rapid, longitudinal evaluation of dietary interventions. In aging nematodes, cholinergic neurons undergo progressive damage without cell loss, a process that mirrors the progressive dendritic, axonal and synaptic degeneration of cholinergic neurons seen in aging humans.

Synchronized worms were fed from their first larval stage for up to 15 days on either B4U 50 or the control strain 168, and their neurons were imaged by fluorescence microscopy on days 3, 7, 11 and 15. Three blinded researchers classified the neurons into three categories: normal neurons showed a continuous, uniform GFP signal along the ventral nerve cord; mildly damaged neurons displayed scattered minor swellings or knots without breaks in fluorescence; and severely damaged neurons showed multiple large swellings or visible ruptures in the nerve cord. From these categories the team calculated a neurodegeneration index, a composite score obtained by weighting normal, mildly damaged and severely damaged neurons with values of 0, 1 and 2 respectively.

The results were striking. Neuronal damage increased progressively with age in all groups, but the decline was markedly more pronounced in worms kept on the control strain: by days 11 and 15 these animals showed a steep drop in the proportion of normal neurons and a higher incidence of both mild and severe defects. Worms continuously fed B4U 50 retained a greater proportion of morphologically intact neurons throughout the observation period, and their neurodegeneration index remained significantly lower. The team also ran dietary switch experiments, transferring worms initially raised on strain 168 to B4U 50 on day 4, day 8 or day 12. Switching early, on day 4, produced a neuroprotective effect comparable to continuous feeding with B4U 50; switching on day 8 still conferred a moderate benefit; but switching on day 12 no longer protected the neurons. This defines a window of early and middle adulthood for optimal dietary intervention.

The researchers also tested whether the bacterial diet could be combined with a known neuroprotective compound. They used TEBONIN intens, a standardized extract prepared from Ginkgo biloba leaves, which has been reported to enhance cognitive performance in patients with mild and moderate dementia and to extend lifespan and alleviate amyloid-beta-induced pathology in C. elegans models. Supplementation with the Ginkgo biloba preparation was neuroprotective in worms fed on either B. subtilis strain, reducing both the occurrence and the timing of mild and severe neuronal defects. Notably, the combination of B4U 50 and the Ginkgo biloba extract yielded the highest proportion of morphologically intact neurons by day 15 and the lowest neurodegeneration index values of any group, while worms on the control strain without the extract fared worst. Representative fluorescence images of day-15 animals made the difference visible: worms receiving the combined intervention displayed largely intact GFP-labeled ventral nerve cords, whereas those fed only the control strain exhibited pronounced swellings and discontinuities.

Why might a biofilm-forming bacterium protect nerve cells? The authors point to a proposed model in which B. subtilis spores ingested with food survive gastric transit, germinate in the intestine, and grow in biofilms that produce and secrete substances spreading from the gut throughout the body, exerting anti-aging and neuroprotective effects. Previous studies have identified the quorum-sensing pentapeptide known as competence sporulation-stimulating factor and the gasotransmitter nitric oxide as key mediators of the benefits of B. subtilis biofilms, and probiotic biofilm-producing strains have been shown to counteract neurodegeneration in wild-type worms as well as in transgenic models of Alzheimer’s and Parkinson’s disease expressing human amyloid-beta and alpha-synuclein. Metabolic remodeling during biofilm development is complex, affecting cellular respiration, lipid metabolism and the production of secondary metabolites and signaling molecules.

The authors are careful about the limits of their work. They did not examine whether B4U 50 actually forms a biofilm inside the worm gut, nor did they identify the specific signaling or metabolic factors mediating the neuroprotective effect, and they note this as a limitation of the study. It is also worth noting that the research was funded by Evonik Operations GmbH, the company that maintains the proprietary B4U 50 strain, and that three of the co-authors are Evonik employees, though the other authors report no competing interests. Nevertheless, the study extends a promising line of research suggesting that B. subtilis strains with strong biofilm proficiency, whether laboratory strains like NCIB3610 or probiotic isolates from East Asian fermented foods, can extend lifespan and protect the nervous system in C. elegans. If the findings translate beyond the nematode, combining biofilm-proficient probiotic bacteria with established natural products such as standardized Ginkgo biloba extract could yield dietary supplements with enhanced neuroprotective capacity for the prevention and amelioration of neurodegenerative disorders.

Subject of Research: Neuroprotective effects of a biofilm-forming Bacillus subtilis probiotic strain on aging cholinergic neurons in C. elegans

Article Title: A Bacillus subtilis strain with high proficiency for biofilm formation delays the onset of aging-associated morphological defects in cholinergic neurons of C. elegans

Article References: Gong, W., Priebs, J., Ohse, V. A., Bremges, A., Dieck, H. T., Klotz, L.-O., Dargatz, M., & Steinbrenner, H. (2026). A Bacillus subtilis strain with high proficiency for biofilm formation delays the onset of aging-associated morphological defects in cholinergic neurons of C. elegans. GeroScience. https://doi.org/10.1007/s11357-026-02594-0

Image Credits: AI Generated

DOI: 10.1007/s11357-026-02594-0

Keywords: Bacillus subtilis, C. elegans, biofilm, cholinergic neurons, neurodegeneration, probiotics, Ginkgo biloba, microbiota-gut-brain axis, aging, nattokinase, neuroprotection, GeroScience