The research team, led by Guido Bocchino of the Catholic University of the Sacred Heart in Rome and including internationally recognized infection specialists such as Javad Parvizi, conducted what is known as an umbrella review. Rather than analyzing individual patient studies, this approach synthesizes existing systematic reviews and meta-analyses, offering a bird’s-eye view of where the published evidence converges and where it falls apart. The researchers searched major bibliographic databases in December 2025, following the PRISMA 2020 reporting guidelines, and ultimately included nine reviews: three systematic reviews and six systematic reviews with meta-analyses. To guard against the double-counting that plagues this type of synthesis, they built a citation matrix of all primary studies and calculated a corrected covered area of 9.4 percent, indicating moderate overlap among the reviews, a finding that shaped how cautiously they interpreted the aggregated numbers.

The headline statistic is striking in its variability. Reported prevalence of culture-negative periprosthetic joint infection ranged from 11.0 percent to 63.6 percent across the included reviews, with a mean of 33.6 percent and a median of 32.5 percent. In other words, depending on which review you consult, somewhere between one in nine and nearly two in three prosthetic joint infections fail to yield a positive culture. The authors attribute this wild spread to differences in patient populations, diagnostic definitions, microbiological workflows, and pre-analytical factors, meaning everything that happens to a specimen before it reaches the culture plate. One large quantitative review reported culture-negative proportions of 38.7 percent across 30 studies, while another meta-analysis found just 11 percent, a gap that underscores how much case mix and laboratory protocol can shift the apparent burden of the disease.

Among the factors driving culture negativity, one stood out repeatedly: prior antibiotic exposure. When patients receive antimicrobial therapy before surgical samples are collected, the drugs suppress bacterial growth in culture even though the infection persists. The reviews that quantified this risk factor reported antibiotic pretreatment in the range of 53 to 64 percent of culture-negative cases, lending strong support to a long-standing principle of antimicrobial stewardship: whenever clinically feasible, antibiotics should be withheld until diagnostic specimens have been obtained. The review also found that culture-negative infections were reported more frequently in the knee than in the hip, accounting for 64.1 percent of cases in the subset of data where joint-specific breakdown was available, and that most studies relied on the Musculoskeletal Infection Society criteria to define the condition, with smaller numbers using Infectious Diseases Society of America or International Consensus Meeting definitions, a patchwork that itself contributes to the heterogeneity.

Into this diagnostic vacuum has stepped a new generation of culture-independent molecular tools, and the umbrella review devoted considerable attention to their performance. Five of the nine included reviews evaluated molecular diagnostics, with next-generation sequencing approaches dominating the landscape. Metagenomic next-generation sequencing, which sequences all genetic material in a specimen without targeting specific organisms, appeared in four of the five molecular-enabled reviews, while targeted sequencing, PCR-based assays, and 16S rRNA sequencing each featured in one. Importantly, no single specimen type emerged as sufficient on its own: synovial fluid, periprosthetic tissue, and sonication fluid, the liquid produced by bathing a removed implant in ultrasound to dislodge biofilm bacteria, were all recurrently evaluated, often in combination, reflecting the understanding that molecular yield depends heavily on sampling strategy.

The diagnostic accuracy figures are impressive on paper. Where meta-analytic estimates were available, pooled sensitivity for molecular methods ranged from 0.81 to 0.93, and pooled specificity ranged from 0.92 to 0.97. In a direct platform comparison, metagenomic next-generation sequencing achieved a sensitivity of 89 percent and a specificity of 92 percent, while targeted next-generation sequencing traded a slightly lower sensitivity of 84 percent for a higher specificity of 97 percent. But the review is equally clear about the caveats. Raw pathogen detection rates among culture-negative cases varied enormously, from 9 percent to 100 percent across individual studies, with pooled summaries clustering around 52 to 54 percent. One review reported shotgun metagenomics detecting pathogens in 43.9 percent of cases while citing upper estimates near 82 percent for sequencing and 90 percent for synovial PCR in selected datasets. The overall false-negative proportion across the evidence base was 21.2 percent, meaning roughly one in five infections still slips past even the most advanced molecular assays.

Perhaps the most revealing finding concerns what molecular testing actually finds when cultures fail. In the one review that detailed post-molecular pathogen attribution, a remarkable proportion of culture-negative infections, around 46 percent, turned out to be fungal, predominantly Candida species, and the assays detected fastidious or atypical organisms including mycobacteria, Cutibacterium acnes, Brucella, and Coxiella burnetii. These are organisms that either grow slowly, require special culture conditions, or are suppressed by prior antibiotics, and their detection supports a conclusion that has been gaining traction in the field: culture-negative status usually reflects microbiological blind spots rather than the absence of any pathogen. Many infections that initially fail to grow in culture later become culture-positive on repeat sampling, suggesting that the true culprit was simply missed the first time around.

Treatment of these infections remains an exercise in empiricism. Because no organism is identified, antibiotic selection relies on guesswork rather than culture-guided targeted therapy. The review found that two-stage exchange, in which the infected implant is removed, an antibiotic-loaded spacer is placed, and a new prosthesis is implanted only after a course of antibiotics, was the most frequently described surgical strategy, accounting for 68.0 percent of the 2,336 extractable procedures across three reviews. Debridement with implant retention accounted for 21.7 percent, and one-stage exchange for 10.3 percent. Vancomycin and cephalosporins were the most commonly mentioned agents, typically providing broad Gram-positive coverage with additional Gram-negative activity, and systemic therapy after revision was often reported as approximately six weeks. Yet dosing, duration, and spacer composition were so inconsistently reported that the authors could not determine whether a two-week antibiotic holiday between stages improves outcomes, a question that recent consensus recommendations have addressed by suggesting continuous therapy may be preferable, particularly for immunocompromised patients.

Outcomes add another layer of complexity. The largest extractable dataset reported an overall failure rate of 19.0 percent for culture-negative infections, with a 95 percent confidence interval of 17.1 to 20.9 percent, while another review found pooled infection control of 79.2 percent. Other syntheses reported treatment success ranging from roughly 70 to 100 percent after two-stage exchange, a spread so wide that direct comparison becomes nearly meaningless. The authors attribute this to inconsistent outcome definitions, differing surgical protocols, and follow-up durations that ranged from three months to ten years. Methodological quality, assessed with the AMSTAR 2 instrument, was similarly variable, with confidence limited by incomplete protocol reporting, variable assessment of publication bias, and insufficient discussion of heterogeneity.

The takeaway from this ambitious synthesis is a call for both humility and better science. Molecular diagnostics, especially next-generation sequencing, are genuinely promising adjunctive tools that can unmask pathogens in a meaningful share of culture-negative cases, but they do not eliminate false negatives, cannot replace phenotypic susceptibility testing, and must be interpreted in the context of prior antibiotics, specimen type, contamination risk, and the overall clinical picture. The authors argue that the first priority remains optimizing conventional culture: obtaining multiple tissue specimens and synovial fluid before antibiotics are given, using appropriate transport and media, prolonging incubation to at least fourteen days, and employing sonication or blood culture bottles where available. Until rigorous primary studies with standardized definitions and reporting are conducted, culture-negative periprosthetic joint infection will remain what it has long been: a common, consequential, and stubbornly opaque challenge at the intersection of surgery and microbiology.

Subject of Research: Culture-negative periprosthetic joint infection: prevalence, molecular diagnostics, treatment, and evidence limitations

Article Title: Culture-negative periprosthetic joint infection: an umbrella review of prevalence, diagnostic strategies, treatment, and methodological limitations

Article References: Bocchino, G., Maccauro, G., Zampoli, A., Papalia, R., Indelli, P. F., Pérez-Prieto, D., & Parvizi, J. (2026). Culture-negative periprosthetic joint infection: an umbrella review of prevalence, diagnostic strategies, treatment, and methodological limitations. Journal of Bone and Joint Infection, 11(4), 479-488. https://doi.org/10.5194/jbji-11-479-2026

Image Credits: AI Generated

DOI: 10.5194/jbji-11-479-2026

Keywords: periprosthetic joint infection, culture-negative infection, next-generation sequencing, metagenomics, joint arthroplasty, molecular diagnostics, antibiotic stewardship, two-stage exchange, biofilm, sonication, umbrella review, orthopedic surgery

The research, led by Belal Abdo and Markus Rupp of the Department of Trauma, Hand and Reconstructive Surgery together with microbiologists at Justus Liebig University Giessen, was published in the Journal of Bone and Joint Infection. The team conducted a retrospective single-center study covering the years 2016 to 2023, screening 287 cases in which explanted osteosynthesis material had been analyzed by sonication. After applying strict inclusion criteria, 157 patients remained in the final analysis. Every included patient had undergone implant removal because of confirmed or suspected fracture-related infection, and every case had results from both peri-implant tissue culture and sonication fluid culture, allowing a direct, paired comparison of the two techniques in the same patients.

The technical logic behind the comparison is straightforward. Peri-implant tissue culture, the current standard, relies on surgeons taking small samples of tissue from immediately around the hardware during revision surgery. These samples are processed in the microbiology laboratory and incubated to see what grows. The weakness of this approach is that biofilm bacteria concentrate on the implant surface itself, not necessarily in the surrounding tissue, and prior antibiotic treatment can suppress growth in culture. False-negative microbiological results occur in up to 35 percent of cases despite clinically manifest infection, according to previous research cited by the authors. Sonication takes a different route: the removed implant is placed in a sterile container filled with 0.85 percent sodium chloride solution and exposed to ultrasound for one minute at 80 percent intensity. The sound waves dislodge biofilm organisms from the metal surface into the fluid, which is then centrifuged, concentrated, and inoculated into a panel of liquid and solid culture media, including aerobic, anaerobic, and fungal media, all incubated for up to 14 days.

The head-to-head results were strikingly balanced. Peri-implant tissue culture detected pathogens in 60.5 percent of the 157 cases, while sonication fluid culture achieved 57.3 percent. Statistically, the difference between the two methods was not significant, a finding confirmed by McNemar’s test for paired binary outcomes. Yet the overlap between the methods was far from complete. Sonication identified additional pathogens that tissue culture had missed in 17.8 percent of cases, while tissue culture uniquely detected organisms in 22.9 percent of cases. When the results of both methods were combined, the overall pathogen detection rate climbed to 70.1 percent. In other words, roughly one in ten additional infections were unmasked simply by running both tests rather than relying on either one alone.

The pathogen spectrum revealed by the two methods overlapped substantially, with methicillin-sensitive Staphylococcus aureus and coagulase-negative staphylococci predominating in both. Most positive cultures were monomicrobial, though polymicrobial growth was observed in 14.4 percent of sonication-positive cases and 21.1 percent of tissue-culture-positive cases, a numerical difference that did not reach statistical significance. Resistant organisms were rare but clinically important: methicillin-resistant Staphylococcus aureus appeared in four cases with each method, and one multidrug-resistant Enterobacterales strain was detected by each approach. The predominance of plate osteosynthesis systems, which accounted for 61.1 percent of removed implants, and screws at 18.5 percent, reflected the typical hardware profile of a trauma center population. The mean patient age was 57.4 years, and late infections occurring more than ten weeks after surgery were the most common presentation at 42.7 percent of cases.

One of the most clinically pressing questions the study addressed was whether prior antibiotic therapy undermines either diagnostic method. At the time of implant removal, 51 of the 157 patients were on ongoing antibiotic treatment or had received antibiotics within the previous 14 days, excluding routine perioperative prophylaxis. The concern is well founded: antibiotics circulating in tissue can suppress bacterial growth in culture, potentially producing misleading negative results. In this cohort, however, ongoing antibiotic therapy was not associated with a statistically significant difference in pathogen detection between the two methods. Tissue culture did show a numerically higher diagnostic yield than sonication among patients receiving antibiotics, but the authors caution that this observation should be interpreted carefully given the limited subgroup size. The finding contrasts with some earlier studies, including work by Dudareva and colleagues, who reported that both methods lost sensitivity after antibiotic exposure, and with the landmark 2007 study by Trampuz and colleagues, which found sonication particularly valuable after prior antibiotics in prosthetic joint infection.

The therapeutic consequences of the microbiological findings may be the most consequential part of the analysis. Antibiotic therapy was actually modified after revision surgery in 47.8 percent of cases. Most of these modifications, 38.9 percent of the entire cohort, were based on concordant findings from both diagnostic methods working together. Only 4.5 percent of patients had their treatment changed exclusively because of sonication results, and an identical 4.5 percent solely because of conventional culture findings. When the researchers asked a slightly different question, namely in how many cases a therapy modification would have been possible on microbiological grounds, the combined findings supported potential adjustment in 93 cases, with 8.3 percent attributable exclusively to sonication and 7.6 percent exclusively to tissue culture. The pattern is clear: the clinical value of each method lies less in replacing the other than in adding pieces to a diagnostic puzzle that neither can complete alone.

These results place fracture-related infection diagnostics in useful context. Sonication has long been an established component of the diagnostic algorithm for periprosthetic joint infection, where multiple studies have shown higher sensitivity than conventional tissue cultures, with reported sonication sensitivities ranging from roughly 52 to 100 percent depending on population and technique. For fracture-related infection, however, the evidence has been more contested. A 2018 systematic review by Onsea and colleagues concluded that sonication fluid culture may serve as a useful adjunct to tissue culture without strong evidence of superiority, and subsequent studies have split on which method performs better. The Giessen data align with the complementary view. Trenkwalder and colleagues similarly reported in 2023 that in septic and aseptic nonunion, sonication fluid culture showed lower sensitivity than tissue culture but higher sensitivity than histopathology, supporting a multimodal approach.

The study is honest about its limitations, and they matter for interpretation. Nearly half of the potentially eligible cases, 130 of 287, were excluded, mostly because they did not meet FRI criteria or because documentation was incomplete during a transition to a new hospital data system, so selection bias cannot be excluded. The retrospective design meant the exact number of intraoperative tissue samples could not always be verified, and because microbiological culture is itself part of the FRI Consensus Definition used as the reference standard, some incorporation bias is unavoidable. The single-center design also limits generalizability. Even so, the central conclusion stands on firm ground: nearly 30 percent of clinically confirmed infections remained culture negative even with both methods combined, underscoring that microbiology must be interpreted within the broader FRI diagnostic framework, which integrates clinical signs, intraoperative findings, histopathology, and culture results.

For surgeons and infectious disease specialists, the practical message is refreshingly concrete. When hardware comes out because of suspected infection, send the implant for sonication and take peri-implant tissue samples, and treat the two results as complementary rather than competing. The combined approach improved pathogen detection irrespective of prior antibiotic exposure, supported targeted antimicrobial management in nearly half of patients, and cost relatively little beyond standard laboratory processing. In an era when biofilm-embedded bacteria routinely defeat single diagnostic tests, the humble strategy of shaking the metal and swabbing the tissue, then reading both answers together, may be the most reliable tool clinicians have for turning invisible infections into treatable ones.

Subject of Research: Diagnostic comparison of implant sonication and peri-implant tissue culture for detecting fracture-related infection

Article Title: Sonication versus peri-implant tissue culture in fracture-related infection: diagnostic performance and therapeutic consequences in a single-center cohort

Article References: Abdo, B., Strack, D., Schäuffele, M., Tüngler, T. L., Imirzalioglu, C., Windhorst, A., Fritzenwanker, M., Heiss, C., & Rupp, M. (2026). Sonication versus peri-implant tissue culture in fracture-related infection: diagnostic performance and therapeutic consequences in a single-center cohort. Journal of Bone and Joint Infection, 11(4), 555-563. https://doi.org/10.5194/jbji-11-555-2026

Image Credits: AI Generated

DOI: 10.5194/jbji-11-555-2026

Keywords: fracture-related infection, sonication, biofilm, peri-implant tissue culture, osteosynthesis, diagnostic sensitivity, antibiotic therapy, orthopedic surgery, implant infection, microbiology, trauma surgery, pathogen detection

The study, published in the journal Results in Chemistry, describes the design and characterization of a lipid nano-emulsion, abbreviated LNE-MP, in which L-DOPA is encapsulated within a blended lipid matrix. Lipid nano-emulsions belong to a broader family of lipid-based nanocarriers that have attracted intense interest in pharmaceutical science because they are biocompatible, biodegradable, and capable of hosting both water-loving and fat-loving drugs. What distinguishes the new work is its deliberate use of natural, sustainable lipid sources rather than synthetic excipients, and its systematic screening of the formulation variables that determine whether the resulting particles are small enough, uniform enough, and stable enough to be medically useful.

The underlying materials logic is elegant. A lipid carrier built purely from solid lipid tends to crystallize into a highly ordered lattice upon cooling, leaving little room for drug molecules to lodge inside. Incorporating a liquid lipid disrupts that ordered packing, creating structural imperfections and voids that can accommodate the drug during recrystallization. Myristic acid, a saturated fatty acid, was chosen as the solid component because it is biocompatible and forms a stable matrix after cooling, and because its free carboxylic group offers polar interaction sites for the hydroxyl, amino, and carboxyl functionalities of L-DOPA, favoring non-covalent drug-lipid association. Palm oil, a sustainable and cost-effective liquid lipid, was selected to supply the disordering fraction of the blend.

Manufacturing the particles involved two sequential steps. First, the lipid mixture, drug, and the nonionic surfactant Tween 80 were subjected to hot homogenization at 1500 revolutions per minute and 55 degrees Celsius for one hour, a temperature safely above the melting point of myristic acid. The resulting coarse emulsion was then refined by ultrasonication, with the team varying sonication time between 40 and 80 minutes and sonication power between 50 and 100 percent. Maltodextrin served as a drying adjuvant during spray drying, converting the liquid nano-dispersion into a structured, storable solid. The screening was conducted sequentially: first the ratio of myristic acid to palm oil was fixed, then surfactant concentration and ultrasonic parameters were tuned.

The ratio screening proved decisive for stability. Formulations with higher proportions of solid lipid, from a 5:5 blend down to 2:8, promoted particle aggregation and phase separation during thermal processing, while pushing the solid fraction below ten percent eroded the mechanical rigidity of the matrix and destabilized the dispersion once again. Only the 1:9 ratio of myristic acid to palm oil yielded a stable dispersion free of coagulation and phase separation after 24 hours of storage, striking the balance between matrix rigidity and liquid-lipid disorder that the colloidal stability of the carrier requires.

With the composition locked in, the processing variables revealed a clear hierarchy of influence. Raising the Tween 80 concentration from 1.5 to 2.0 percent had a more dramatic effect on particle size than any adjustment of sonication, driving the mean diameter from around 110 nanometers down to the 81 to 91 nanometer range. The surfactant lowers surface tension, stabilizing the spherical droplets formed during ultrasonic cavitation before they can recoalesce. The finest and most uniform product, with a mean size of roughly 85 to 86 nanometers and a polydispersity index as low as 0.10, emerged from the combination of 2 percent Tween 80, 80 minutes of sonication, and 50 percent power. Notably, excessive energy input was counterproductive: higher sonication power broadened the size distribution, because intense cavitation can fragment droplets only for them to remerge.

Characterization confirmed that the optimized particles were not merely small but colloidally robust. The zeta potential, a measure of surface charge, came in at approximately minus 40 millivolts, well beyond the minus 30 millivolt threshold generally associated with strong electrostatic repulsion between droplets and high physical stability in nanosuspensions. The negative charge arises from the ionization of acidic groups in the lipid components and the orientation of the nonionic surfactant at the particle surface, which generates an electrical double layer. In drug delivery, a moderately high negative surface charge carries a further advantage: it tends to reduce nonspecific protein adsorption and opsonization compared with cationic particles, potentially extending circulation time and improving biocompatibility.

Spectroscopy and microscopy filled in the molecular picture. Fourier transform infrared spectra of the loaded particles retained the characteristic aliphatic carbon-hydrogen stretches near 2920 to 2850 wavenumbers and the ester carbonyl band near 1740 to 1750 wavenumbers of the lipid matrix, indicating that the carrier’s chemical structure survived formulation intact. Meanwhile, the hydroxyl and amine bands characteristic of pure L-DOPA broadened and shifted in the loaded formulation, evidence that the drug’s functional groups engage in non-covalent interactions with the lipids. Crucially, no new absorption bands appeared, suggesting no chemical transformation of the drug within the sensitivity of the technique. Transmission electron microscopy showed nearly spherical particles with low aspect ratio and little clustering, consistent with the light-scattering data, while energy-dispersive X-ray spectroscopy detected only carbon, oxygen, and nitrogen, in approximate atomic proportions of 72, 25, and 3 percent, the nitrogen being the fingerprint of incorporated L-DOPA and the absence of other elements confirming high chemical purity.

Functionally, the formulation encapsulated roughly half of the initial L-DOPA payload, an efficiency the authors acknowledge will require further optimization if higher loading is pursued. The release behavior, however, is where the design shows its therapeutic promise. In dialysis-bag experiments conducted over eight hours, cumulative release climbed to about 27 percent at the intestinal pH of 7.4 and about 20 percent at the gastric pH of 1.2 after six hours, with no sudden burst release at either condition. The higher release at physiological pH reflects the differing solubility and ionization of L-DOPA and pH-dependent hydration of the particle surface. Kinetic modeling showed the profile fit a zero-order model best at pH 7.4, meaning release was governed more by the structural characteristics of the lipid carrier than by the remaining drug concentration, exactly the behavior desired for smoothing plasma fluctuations and reducing dosing frequency. The Korsmeyer-Peppas diffusion exponents fell in the anomalous transport range, though the authors treat that interpretation as preliminary given the model’s weaker fit.

The work remains at the in vitro stage, and the authors themselves note that chromatographic verification by high-performance liquid chromatography and additional solid-state studies by differential scanning calorimetry and X-ray diffraction are needed before the platform can advance. Even so, the demonstration that a sub-100-nanometer, narrowly distributed, electrostatically stabilized L-DOPA carrier can be built from myristic acid and palm oil, two cheap and abundant natural feedstocks, using nothing more exotic than homogenization and sonication, is a meaningful contribution to affordable nanomedicine. For a disease whose prevalence is rising steeply and whose patients depend on precise, steady dopaminergic dosing, a delivery platform that promises sustained release, reduced peripheral waste, and improved tolerability, manufactured from sustainable ingredients, offers a compelling glimpse of where Parkinson’s pharmacotherapy may be heading next.

Subject of Research: Lipid nano-emulsion formulation of myristic acid and palm oil for L-DOPA delivery in Parkinson's disease

Article Title: Efficient delivery of L-DOPA through lipid nano-emulsion formulation using solid myristic acid and liquid palm oil

Article References: Sardjono, R. E., Chyntia, A., Nuraini, V. A., Gunawan, R., Kadarohman, A., Ray, H. R. D., Vikasari, S. N., Erdiwansyah, Fatimah, S., & Ko, Y. G. (2026). Efficient delivery of L-DOPA through lipid nano-emulsion formulation using solid myristic acid and liquid palm oil. Results in Chemistry, 31, Article 103937. https://doi.org/10.1016/j.rechem.2026.103937

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103937

Keywords: L-DOPA, lipid nano-emulsion, myristic acid, palm oil, Parkinson's disease, drug delivery, nanoparticles, encapsulation efficiency, zeta potential, controlled release, Tween 80, sonication