The research team, led by Bakhtawar Fatima and Adeel Mahmood of Government College Women University in Sialkot, together with colleagues from institutions in Pakistan and Saudi Arabia, collected surface-water samples from ten monitoring sites representing upstream, midstream, and downstream reaches of the river during a post-monsoon sampling campaign. This design allowed the investigators to trace how antibiotic loads change as the river moves through populated and agricultural terrain. Post-monsoon sampling is particularly informative because seasonal runoff can mobilize contaminants from soils, wastewater outfalls, and livestock areas, delivering a snapshot of the pollution burden after peak hydrological activity.

Analytically, the study targeted six antibiotics spanning several drug classes: azithromycin, a macrolide; ofloxacin, ciprofloxacin, and levofloxacin, all fluoroquinolones; linezolid, an oxazolidinone; and cefixime, a cephalosporin. These compounds were quantified using high-performance liquid chromatography coupled with photodiode-array detection, a technique that separates complex environmental mixtures and identifies compounds by their characteristic light absorption spectra. The measured concentrations followed a clear hierarchy: azithromycin at 20.30 micrograms per liter, ofloxacin at 12.70, ciprofloxacin at 8.03, linezolid at 4.55, cefixime at 1.40, and levofloxacin at 0.51 micrograms per liter.

The dominance of azithromycin is significant for several reasons. Macrolide antibiotics are known to persist in aquatic environments and are frequently reported at elevated levels in rivers across Asia, as global reviews of macrolide contamination in surface waters have documented. Azithromycin consumption surged during the COVID-19 pandemic, and researchers in Pakistan have separately reported increased antimicrobial resistance against the drug during that period, attributing it in part to irrational utilization. The new Jhelum data suggest that heavy use of this class is leaving a chemical fingerprint in the river system, with azithromycin showing the greatest pollution burden across all monitoring sites investigated, while levofloxacin exhibited comparatively limited contamination.

To characterize the overall contamination pattern, the team applied two complementary assessment frameworks. Single-factor pollution indices evaluate each antibiotic individually against reference thresholds, while a comprehensive pollution index aggregates the contributions of all six compounds into a single measure of combined contamination. According to the comprehensive assessment, the investigated river transect carries substantial combined antibiotic pollution. The researchers then used GIS-based spatial interpolation to visualize how contamination is distributed across the river’s length, a technique that converts discrete measurements from ten sampling points into a continuous surface showing pollution gradients between upstream, midstream, and downstream reaches.

The ecological risk assessment produced the study’s most striking result. Using risk quotient analysis, a screening approach that compares measured environmental concentrations with predicted no-effect concentrations for aquatic organisms, azithromycin yielded the highest ecological risk quotient of 17.41. A risk quotient above one signals high predicted ecological risk under the applied screening framework, so a value exceeding seventeen indicates that the concentrations found in the Jhelum are far above levels considered safe for aquatic life. Fluoroquinolones such as ofloxacin and ciprofloxacin, which also registered elevated concentrations, are similarly associated with concerns for aquatic organisms, including effects on photosynthetic microbes and invertebrates that form the base of riverine food webs.

The ecological implications extend beyond individual toxicity. Antibiotic residues in surface water exert selective pressure on bacterial communities, promoting the proliferation of antibiotic resistance genes that can move between environmental and clinical settings. Research on swine farming, for example, has shown elevated proliferation of resistant bacteria and resistance genes in groundwater connected to agricultural areas. Short-term exposure to antibiotics has also been shown to cause long-term disturbance in gut microbial metabolism and molecular ecological networks, underscoring how persistent low-level contamination can reorganize microbial ecosystems. In a river like the Jhelum, which supports fisheries, irrigation, and domestic water use along its course, such microbial shifts carry consequences for both biodiversity and public health.

On the human health side, the picture is more reassuring, at least under the screening assumptions applied. The team calculated hazard quotients for non-carcinogenic risks, and all values remained below unity, the threshold that would indicate potential concern. This means that, based on the measured concentrations and standard exposure assumptions, the antibiotic residues in the river water do not currently pose significant non-carcinogenic health risks to people. The authors are careful to frame this as a screening-level result; hazard quotients near or below one do not eliminate concerns about chronic low-dose exposure, mixture effects, or the indirect pathway through antimicrobial resistance, which the World Health Organization identifies as one of the top global public health threats.

The Jhelum findings fit into a broader pattern documented across South Asia and beyond. Reviews of antibiotic contamination in the major river systems of South Asian countries, studies of urban rivers in northwest Pakistan, and a landmark global assessment of pharmaceutical pollution of the world’s rivers published in the Proceedings of the National Academy of Sciences all point to the same conclusion: pharmaceutical residues in waterways are a planetary problem, with the highest concentrations typically found in low- and middle-income countries where wastewater treatment infrastructure lags behind pharmaceutical consumption. Pakistan’s national antimicrobial consumption data show significant trends before and after the COVID-19 pandemic, adding context to the residues now detected in its rivers.

The authors argue that their findings strengthen the case for improved wastewater management, pharmaceutical discharge controls, and systematic monitoring of antibiotic residues in the River Jhelum. Because conventional wastewater treatment plants are often not designed to remove pharmaceutical compounds, effluents can pass through treatment and enter rivers largely intact. Targeted interventions, such as upgraded treatment technologies, take-back programs for unused medications, stewardship of antibiotic prescribing in human and veterinary medicine, and routine surveillance at fixed monitoring stations, would together reduce the input of these emerging contaminants. The study, funded through a large research project at King Khalid University in Saudi Arabia, provides a baseline against which future monitoring can measure whether such interventions are working, and it adds the River Jhelum to the growing map of the world’s antibiotic-contaminated waterways.

Subject of Research: Occurrence, spatial distribution, and ecological and human health risks of antibiotic residues in the River Jhelum, Pakistan

Article Title: Occurrence, spatial distribution, and ecological and human health risks of antibiotic residues in the River Jhelum

Article References: Fatima, B., Mahmood, A., Urooj, A., Waseem, A., Mahmood, A., Ullah, R., Alamri, S., Irfan, H. M., & Mahmood, A. (2026). Occurrence, spatial distribution, and ecological and human health risks of antibiotic residues in the River Jhelum. Environmental Geochemistry and Health, 48(16), Article 643. https://doi.org/10.1007/s10653-026-03539-4

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03539-4

Keywords: antibiotic residues, River Jhelum, Pakistan, azithromycin, ecological risk, human health risk assessment, antimicrobial resistance, emerging contaminants, surface water pollution, HPLC, GIS spatial analysis, wastewater management

The review, led by Qiaochun Lu and colleagues at Zhejiang University School of Medicine and partner institutions in China, systematically evaluates both the clinical and mechanistic evidence for beta-lactam–macrolide combination therapy. The authors apply a three-level grading framework to distinguish established findings from probable or merely hypothesized ones. Their central conclusion is nuanced: the combination shows its clearest benefit in adults with severe community-acquired pneumonia, while evidence in non-severe pneumonia and pediatric populations remains inconsistent. Biological synergy, they caution, does not automatically translate into clinical benefit for every patient.

The strongest clinical signal comes from severe community-acquired pneumonia. In the double-blind ACCESS trial, adjunctive clarithromycin added to a beta-lactam significantly improved a composite early endpoint combining symptom reduction and inflammatory markers, reduced new organ failure, and shortened time to discharge alive. A subsequent meta-analysis of randomized trials estimated higher clinical success with macrolide add-on therapy, and a network meta-analysis ranked beta-lactam plus macrolide favorably among empirical strategies for severe disease. Yet the mortality benefit remains suggestive rather than definitive, derived largely from observational data vulnerable to confounding by illness severity and treatment timing.

Outside severe pneumonia, the picture is far less favorable. The cluster-randomized CAP-START trial found beta-lactam monotherapy noninferior to combination strategies for 90-day mortality in non-ICU wards, and an open-label randomized trial in moderately severe pneumonia failed to establish monotherapy inferiority. Pediatric cohort data, including a study of more than 2,500 hospitalized children, showed no routine outcome benefit from empirical macrolide combination therapy. Guidelines reflect this unevenness: the 2019 ATS/IDSA recommendations support the combination for hospitalized and severe pneumonia, while the 2023 European guideline conditionally favors adding a macrolide over a fluoroquinolone in severe disease but rates the evidence as very low certainty.

What explains the apparent synergy at the mechanistic level? The review identifies several complementary pathways. The most established is target complementarity: beta-lactams inhibit peptidoglycan crosslinking while macrolides block translation, so the two drugs attack distinct essential processes simultaneously. A second, more speculative hypothesis holds that beta-lactam-induced cell-wall injury increases macrolide penetration into the bacterial cell. Evidence for this comes from indirect models, such as bacteriophage-derived endolysins that disrupt peptidoglycan and enhance macrolide activity, but direct demonstration with conventional clinical combinations is lacking.

Additional mechanisms operate at subinhibitory concentrations. In vitro studies show that azithromycin downregulates the MexAB-OprM efflux pump in Pseudomonas aeruginosa and suppresses quorum-sensing signals of the las and rhl systems, reducing production of virulence factors such as elastase, rhamnolipids, and pyocyanin. In serial-passage and animal models, azithromycin repressed translation of the stress-response regulator rpoS and delayed emergence of resistance to ceftazidime-avibactam. Macrolides also alter biofilm matrix composition and alginate production, potentially exposing proliferating bacteria to beta-lactam activity. These findings lend biological plausibility to the combination but remain largely preclinical.

Host-directed effects may be equally important. In the ACCESS trial, clarithromycin modulated tumor necrosis factor-alpha responses in stimulated immune cells and altered circulating interleukin-10 and the IL-8/IL-10 balance, suggesting correction of infection-related immune dysregulation. Preclinical work indicates macrolides can dampen pro-inflammatory macrophage activation, promote an M2-like phenotype with enhanced phagocytosis, and influence dendritic-cell and T-cell responses. The authors grade cytokine modulation as supported by patient-derived data, while broader immune effects remain probable based on animal and ex vivo evidence.

The review also emphasizes that the three macrolides are not interchangeable. Clarithromycin carries the only direct randomized evidence from the ACCESS trial, which cannot be extrapolated to azithromycin or erythromycin. Azithromycin’s combination evidence is essentially preclinical, and its use in pneumonia regimens rests primarily on atypical-pathogen coverage rather than proven synergy. Erythromycin has virtually no contemporary evidence for acute combination therapy and is limited by gastrointestinal intolerance and strong CYP3A4 inhibition. All macrolides can prolong the QT interval, and large pharmacoepidemiologic studies have linked macrolide therapy to elevated cardiovascular risk, although the ACCESS trial itself found no increase in adverse events.

Resistance considerations further complicate the picture. erm-mediated ribosomal methylation generally abolishes macrolide activity, and a beta-lactam partner cannot restore susceptibility, a critical point when atypical coverage is the goal. Macrolide exposure also selects for resistance in colonizing microbiota and environmental reservoirs. The authors advocate an antibiotic time-out at 48 to 72 hours, using clinical response and microbiological findings to de-escalate to beta-lactam monotherapy once atypical infection becomes unlikely. Pharmacokinetic differences matter too: beta-lactams require sustained concentrations above the minimum inhibitory concentration, while macrolides achieve high tissue levels with prolonged post-antibiotic effects, a complementarity that may support combination use in severe disease.

The reviewers conclude that beta-lactam–macrolide therapy is a biologically and clinically defensible option for selected severe infections, particularly severe community-acquired pneumonia, but not a universally synergistic strategy. Most proposed molecular pathways are pathogen- and exposure-specific, and several remain hypothetical. Future research should link defined drug exposures and pathogen-specific mechanisms to patient-centered outcomes, stratified by severity, macrolide agent, and resistance phenotype. Until then, the combination should be reserved for the right patients, at the right time, with the right drugs—rather than extrapolated indiscriminately across the infectious-disease spectrum.

Subject of Research: Mechanisms and clinical evidence for synergistic interactions between macrolide and beta-lactam antibiotics in bacterial infections

Article Title: Mechanistic insights into the synergistic interactions between macrolides and beta-lactams in bacterial infections

Article References: Lu, Q., Qian, X., Li, Y., Liu, Y., Chen, Z., He, L., Yu, Y., Jin, Z., & Shi, Y. (2026). Mechanistic insights into the synergistic interactions between macrolides and beta-lactams in bacterial infections. Frontiers in Cellular and Infection Microbiology, 16, Article 1894766. https://doi.org/10.3389/fcimb.2026.1894766

Image Credits: AI Generated

DOI: 10.3389/fcimb.2026.1894766

Keywords: macrolides, beta-lactams, antibiotic synergy, community-acquired pneumonia, clarithromycin, azithromycin, antimicrobial resistance, biofilms, quorum sensing, immunomodulation, pharmacokinetics, antibiotic stewardship

Researchers at the University of Tennessee College of Veterinary Medicine, working with the Gastrointestinal Laboratory at Texas A&M University, enrolled twelve healthy research colony Beagles with no history of gastrointestinal signs and no antimicrobial exposure for at least six months. One dog was excluded early after developing acute intervertebral disc disease unrelated to the trial, leaving eleven animals for analysis. Each dog received azithromycin at 2 mg/kg by mouth every eight hours for eight days, a regimen corresponding to roughly one-half to one-fifth of the dose used for antimicrobial purposes. Fecal samples were collected at baseline, during treatment, and at multiple points across a five-week recovery window, with daily fecal scoring throughout the 45-day study. All dogs acted as their own controls, a design considered appropriate given the well-established temporal stability of the canine fecal microbiome.

The analytical approach combined quantitative PCR measurement of sixteen core bacterial taxa with a validated Dysbiosis Index, the only analytically validated assay for fecal dysbiosis in dogs and cats. In parallel, twenty-nine conjugated, unconjugated, and oxo-isoforms of primary and secondary bile acids were quantified using liquid chromatography-tandem mass spectrometry. The choice of bile acids was not arbitrary. Bile acid metabolism is one of the most sensitive functional readouts of gut microbial health, because a single bacterial species, Peptacetobacter hiranonis, performs the critical conversion of primary bile acids into secondary forms through enzymes encoded by the bai operon. When that conversion falters, it signals more than a shift in microbial census: it signals a loss of metabolic function with potential consequences for the entire intestinal ecosystem.

The results confirmed the researchers’ hypothesis with striking clarity. Even at the reduced prokinetic dose, azithromycin triggered measurable dysbiosis. By day six, the abundances of seven of sixteen core taxa had fallen significantly, including P. hiranonis, Faecalibacterium, and Fusobacterium, three of the most functionally important members of the canine gut community. Faecalibacterium produces short-chain fatty acids that fuel the cells lining the intestine and modulate mucosal immunity, while Fusobacterium is a major butyrate producer that ferments amino acids rather than carbohydrates. P. hiranonis dropped dramatically, with median abundance falling from roughly 6.65 to 1.77 log DNA per gram of feces during treatment. Fecal scores also rose significantly during administration, though they remained within the normal range, suggesting at most a mild, transient loosening of stool.

The metabolic consequences followed directly from the microbial losses. By day eleven, the percentage of primary unconjugated bile acids had risen significantly, with a median of about 94 percent in the most affected animals, while secondary bile acids, lithocholic acid and deoxycholic acid, declined sharply. The strength of the relationship was remarkable: the increase in primary bile acids correlated negatively with P. hiranonis abundance at a coefficient of -0.936, a near-perfect inverse association. This tight coupling makes physiological sense. With the bacterium that performs 7-alpha-dehydroxylation suppressed, primary bile acids accumulated unconverted. Because elevated primary bile acids can stimulate colonic water secretion and alter mucosal permeability, the authors speculate that this metabolic shift may even have contributed to the mild increase in fecal scores observed during treatment.

The good news is that the damage was largely temporary. By day twenty-six, P. hiranonis had normalized in all but one dog, and every animal had recovered by day thirty-six. Fecal bile acid proportions returned to baseline by day forty-five. Of the nine taxa significantly altered by the drug, eight bounced back within the study window. This recovery pattern contrasts favorably with previously published work on tylosin and metronidazole, where sustained elevations in primary bile acids have been documented in individual dogs for up to eight weeks. The authors note, however, that their recovery measurements may have been flattered by the sampling schedule, since bile acids were only measured on days eleven and forty-five, leaving the exact timing of metabolic recovery unknown.

One finding stood out as genuinely atypical. Streptococcus, a group of gram-positive commensals that usually flourishes during dysbiosis thanks to its tolerance of the acidic, substrate-rich conditions antibiotics create, instead declined significantly by day eleven and never recovered for the duration of the study. The pattern defies the standard ecological script. The authors ruled out simple pharmacokinetic explanations: azithromycin’s reported half-life in dogs ranges from 51 to 90 hours, meaning the drug should have been fully eliminated within about nineteen days, and post-antibiotic effects last only hours. The most plausible explanation, they argue, is a lasting ecological disruption within the fecal microbiome, one whose clinical significance in healthy dogs remains uncertain but which deserves attention in future work.

Equally unexpected was the absence of Escherichia coli overgrowth, a hallmark response to metronidazole, tylosin, and amoxicillin in dogs. The researchers attribute this to azithromycin’s distinctive macrolide structure, which confers higher basicity and greater intracellular uptake, enhancing its activity against Enterobacteriaceae. In human medicine, the drug demonstrates excellent activity against common enteropathogenic strains of E. coli. This pharmacological idiosyncrasy also helps explain why the Dysbiosis Index, which normally rises sharply after antibiotic exposure, increased only modestly in this study. Because the two taxa that typically drive the index upward, E. coli and Streptococcus, both decreased instead, the index understated the true extent of dysbiosis. The authors emphasize that the tool must always be interpreted alongside the abundances of all core bacteria, since clear functional change was evident even when the composite score appeared reassuring.

Clinically, the study offers a measured but important message. Short-term low-dose azithromycin was well tolerated in healthy dogs, with no gastrointestinal adverse effects, no changes in body weight or body condition, and normalization of nearly every disturbed parameter within five weeks. Yet the authors caution against extrapolating too readily to the clinic. Healthy research Beagles do not represent the dogs that would actually receive the drug as a prokinetic, and animals with pre-existing dysbiosis, altered bile acid metabolism, or chronic enteropathy could respond very differently. Antimicrobial resistance, which was not evaluated here, remains an additional consideration whenever an antibiotic is deployed for a non-antimicrobial purpose. The prokinetic efficacy of azithromycin in dogs, moreover, has never been rigorously proven, so future dosing strategies may differ from the one tested. What the study establishes is a proof of principle: even at doses one-fifth of those used against infection, azithromycin is not microbiologically silent. It remodels the gut ecosystem and disrupts one of its most essential metabolic functions, and it does so in a pattern that is mostly, though not entirely, reversible. For veterinarians weighing the drug against alternatives, and for researchers designing the next generation of prokinetic trials, that evidence now exists.

Subject of Research: Effects of low-dose azithromycin on the fecal microbiome and fecal bile acids in healthy dogs

Article Title: Effect of low dose azithromycin on the fecal microbiome and fecal bile acids in healthy dogs

Article References: Smith, C., Husnik, R., Gaschen, F., Kirk, C., Zhu, X., & Suchodolski, J. (2026). Effect of low dose azithromycin on the fecal microbiome and fecal bile acids in healthy dogs. Journal of Veterinary Internal Medicine, 40(5), Article aalag220. https://doi.org/10.1093/jvimsj/aalag220

Image Credits: AI Generated

DOI: 10.1093/jvimsj/aalag220

Keywords: azithromycin, dogs, microbiome, bile acids, dysbiosis, prokinetics, Peptacetobacter hiranonis, veterinary medicine, qPCR, gut health, macrolides, Streptococcus

Scrub typhus is caused by Orientia tsutsugamushi, an obligate intracellular bacterium transmitted to humans through the bite of infected larval mites, commonly called chiggers. The disease is a major public health problem across the Asia-Pacific region, from Japan and Korea through Southeast Asia to northern Australia and the Indian subcontinent, with an estimated one million cases annually. Classically, infection produces a fever, headache, and a distinctive skin lesion known as an eschar, a dark, necrotic scab that forms at the site of the mite bite. The eschar is one of the most useful diagnostic signs in older children and adults. But in neonates, as the new report makes clear, the lesion may be entirely absent, stripping clinicians of the single most recognizable feature of the disease and leaving a nonspecific picture of fever and sepsis-like deterioration that can easily be mistaken for bacterial sepsis or meningitis.

The three infants described in the series all presented during the second to fourth week of life, an age when neonatal sepsis is a constant concern in any neonatal intensive care unit. Each of them showed involvement of multiple organ systems, and each displayed neurological manifestations, ranging in severity from encephalitic signs to seizures. Notably, none of the three had a typical eschar, which is precisely the feature that usually allows clinicians in endemic regions to suspect scrub typhus at the bedside. Without that sign, the infants’ illnesses looked like any number of other neonatal emergencies, and the correct diagnosis might have remained elusive without advanced molecular testing.

An intriguing epidemiological thread runs through all three cases. In retrospect, all three mothers reported having been diagnosed with scrub typhus during their pregnancies. However, the authors are careful to note that none of these maternal histories could be independently verified, because the original medical records and laboratory results from the mothers’ illnesses were unavailable. This distinction matters enormously for what the cases can and cannot tell us about how the babies were infected. A maternal history of scrub typhus during pregnancy raises the possibility of transplacental transmission of Orientia tsutsugamushi from mother to fetus, a route of infection that has been suggested in the literature but remains difficult to prove. The authors explicitly state that their data do not establish transplacental transmission, and they emphasize that postnatal acquisition, through mite bites after birth, cannot be excluded. In other words, the shared maternal histories are an important clue, but not a demonstration of congenital infection.

One of the three cases offers a particularly striking natural experiment. The affected infant was one member of a dichorionic diamniotic twin pair, meaning the twins developed from two separate fertilized eggs with separate placentas and separate amniotic sacs. While one twin fell gravely ill, the co-twin remained completely asymptomatic, and targeted genetic testing of both blood and cerebrospinal fluid from the healthy twin came back negative for Orientia tsutsugamushi. This discordance is fascinating from a transmission standpoint. If the infection had been acquired transplacentally, one might have expected both twins to be at risk, although separate placentas could in principle lead to separate outcomes. If the infection was acquired postnatally through a mite bite, discordance would be less surprising. The twin case therefore illustrates exactly why the authors resist drawing firm conclusions about the route of transmission from their small series.

The neurological dimension of these cases deserves particular attention. Two of the three infants had strong evidence of central nervous system involvement, while the third developed seizures in the context of severe systemic illness accompanied by major metabolic disturbances, a situation in which seizures can arise from metabolic derangement rather than direct infection of the brain. Central nervous system involvement in scrub typhus is recognized in older patients, where the organism can cause meningitis or encephalitis, but documenting it in neonates is exceptionally rare. The report suggests that when scrub typhus strikes newborns, the brain may be a frequent target, and that neurological signs in a febrile neonate from an endemic region should prompt consideration of this diagnosis alongside the usual suspects.

Establishing the diagnosis in these cases depended on next-generation sequencing, a family of molecular techniques that can detect the genetic material of pathogens in clinical samples without requiring the organism to be cultured or targeted with specific tests. In one patient, Orientia tsutsugamushi was detected using blood metagenomic next-generation sequencing, an unbiased approach that sequences all genetic material in a sample and identifies pathogens by matching the results against databases. In the other two patients, the diagnosis came from targeted next-generation sequencing of blood and, in some cases, cerebrospinal fluid. This technological angle is one of the most important practical lessons of the report. Routine investigations in neonatal sepsis, including blood cultures, are often unrevealing in scrub typhus because Orientia is an intracellular bacterium that is difficult to culture, and serological tests, the mainstay of diagnosis in adults, may be unreliable in the earliest days of infection. Molecular testing may establish an etiological diagnosis precisely when conventional methods come up empty.

The outcomes in the series were starkly divided. One infant recovered after treatment with azithromycin followed by doxycycline, the macrolide and tetracycline-class antibiotics that are the standard therapies for scrub typhus. The other two infants died after progressive multiorgan dysfunction. The survival of the treated infant underscores a point that infectious disease specialists have long emphasized for scrub typhus in general: the infection is treatable, and early appropriate antibiotic therapy can be lifesaving, but delays in diagnosis allow the organism to drive escalating inflammation, coagulopathy, liver injury, and organ failure. In neonates, where clinical deterioration can be rapid and nonspecific, the window for effective intervention may be especially narrow, which makes clinical suspicion and rapid diagnostic workup all the more critical.

The authors draw a clear set of practical conclusions for clinicians working in endemic areas. Neonatal scrub typhus can cause life-threatening multisystem disease and may involve the central nervous system. In regions where the disease circulates, it should be considered in any neonate with unexplained fever, sepsis-like illness, thrombocytopenia, which is a low platelet count, coagulopathy, liver injury, or neurological manifestations, even in the complete absence of an eschar. This expanded case definition is significant because it shifts scrub typhus from a diagnosis that depends on a visible skin lesion to one that depends on pattern recognition and laboratory confirmation. A retrospectively reported maternal history of scrub typhus during pregnancy, even when unverifiable, should be treated as an important epidemiological clue that lowers the threshold for molecular testing.

Beyond the immediate clinical lessons, the case series highlights gaps that future research will need to fill. The question of whether Orientia tsutsugamushi can cross the placenta and infect the fetus remains open, and well-documented twin pregnancies, prospective maternal cohorts in endemic regions, and systematic molecular testing of neonates with sepsis-like illness could all help resolve it. The report also illustrates the growing role of metagenomic and targeted sequencing in neonatal intensive care, where rapid, unbiased pathogen detection can make the difference between a correct diagnosis and a fatal blind spot. For now, the message from Yunnan is straightforward: in the mite-endemic belt that spans much of Asia, the youngest and most vulnerable patients can fall victim to scrub typhus, and the absence of the disease’s most famous sign should never be taken as reassurance.

Subject of Research: Neonatal scrub typhus with neurological manifestations caused by Orientia tsutsugamushi

Article Title: Neonatal scrub typhus with neurological manifestations: a case series from an endemic region

Article References: Yu, X., Li, J., Yang, P., Song, Y., Xi, M., Cui, S., Zhanghuang, C., & Liu, L. (2026). Neonatal scrub typhus with neurological manifestations: a case series from an endemic region. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14578-8

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14578-8

Keywords: scrub typhus, Orientia tsutsugamushi, neonates, central nervous system infection, next-generation sequencing, Yunnan Province, neonatal sepsis, eschar, transplacental transmission, doxycycline, azithromycin, case series

The study drew on the Child Health with Azithromycin Trial, known as CHAT, a placebo-controlled cluster randomized trial conducted in Burkina Faso in which entire communities were assigned, in a one-to-one ratio, to receive twice-yearly azithromycin or a matching placebo for children aged one to 59 months. The original trial was designed to test whether the antibiotic could prevent deaths from any cause, extending to a high-mortality African setting the earlier evidence from the landmark MORDOR trial in Niger, Malawi, and Tanzania, which had demonstrated a significant reduction in all-cause child mortality with mass drug administration.

The research team, led by investigators at the University of California, San Francisco and the Centre de Recherche en Santé de Nouna in Burkina Faso, asked a deceptively simple question: if azithromycin works by clearing infections, and if infections sap children’s growth, shouldn’t treated children grow better? To answer it, they tracked two standard measures of undernutrition. The first was mid-upper arm circumference, or MUAC, a tape measurement of the upper arm that is widely used in field settings to screen for acute malnutrition because it changes little with age in early childhood and requires no scales. The second was the weight-for-age Z-score, or WAZ, a statistical measure of how far a child’s weight deviates from the expected weight for a healthy child of the same age and sex, calculated here for infants aged one to eleven months.

The scale of the analysis was considerable. The researchers included 80,282 children aged one to 59 months, of whom 26,983 were infants in the one-to-eleven-month age range, drawn from 284 communities. Measurements were collected every six months over the course of the trial, with MUAC taken in all children and weight recorded in infants both to calculate weight-based drug dosing and to enable the nutritional analysis. Because communities rather than individuals were randomized, the statistical methods accounted for clustering, comparing outcomes between the azithromycin and placebo arms at the community level and also following individual children longitudinally over time.

The results were unambiguous in their null finding. At the community level, after 36 months of intervention there was no evidence of any difference in mean MUAC or mean WAZ between villages that had received azithromycin and those that had received placebo. Nor was there any divergence over time: the change in MUAC over the follow-up period showed no difference between arms, with a P-value for interaction of 0.94, and the change in WAZ similarly showed no difference, with a P-value of 0.18. In plain terms, children in azithromycin communities did not have measurably better arm circumference or weight gain than children in placebo communities, either on average or in their growth trajectories.

These findings matter because they speak directly to the leading hypothesis about how mass azithromycin saves lives. The drug, a long-acting macrolide antibiotic, is known to treat a broad range of bacterial infections and some intracellular pathogens, including subclinical infections that never announce themselves with fever or clinic visits. Researchers have plausibly argued that reducing this invisible infectious burden could free up calories and nutrients that would otherwise be diverted to immune defense, allowing children to grow better and thereby lowering their vulnerability to severe illness and death. Undernutrition and infection form a well-documented vicious cycle in early childhood: infection suppresses appetite and impairs nutrient absorption, while malnutrition weakens immune defenses and increases the severity of subsequent infections. Breaking that cycle at the infection end, the reasoning went, should improve the nutrition end.

The CHAT nutritional analysis suggests it did not, at least not in this setting. One interpretation is that the infections most responsible for azithromycin’s mortality benefit are acute, severe episodes rather than the chronic, growth-slowing burden that shapes anthropometric measures over months and years. Mortality in these settings is often driven by rapidly progressive infections such as pneumonia, sepsis, and malaria-associated bacterial coinfections, which can kill a child long before any nutritional pathway could come into play. If azithromycin primarily prevents these fulminant events, its effect on growth would be expected to be small or absent, exactly what the trial observed.

Another possibility is that the dominant drivers of undernutrition in Burkina Faso lie outside the reach of a twice-yearly antibiotic. Diarrheal disease from enteric pathogens, environmental enteric dysfunction driven by repeated exposure to fecal contamination, dietary insufficiency, and malaria are all entrenched in the region, and a macrolide given twice a year may not durably suppress the microbial ecology that stunts growth. Some of the pathogens that most strongly depress growth, such as certain enteroviruses and parasites, are not susceptible to azithromycin at all. The drug’s effects on the gut microbiome, moreover, are complex, and repeated exposure has been associated with rising antimicrobial resistance, a concern that weighs on any expansion of mass distribution programs.

For policymakers, the analysis does not undermine the case for mass azithromycin where mortality benefits have been demonstrated, but it does sharpen the picture of what the intervention can and cannot do. Countries weighing twice-yearly distribution should not expect it to serve as a nutrition program, and investments in the established tools of nutrition improvement, including infant and young child feeding, micronutrient supplementation, food security, and water, sanitation, and hygiene infrastructure, remain essential alongside any antibiotic strategy. The finding also redirects scientific attention toward identifying the actual biological mechanisms behind the mortality reduction, whether through targeted studies of severe infection incidence, biomarkers of systemic inflammation, or cause-of-death ascertainment in future trials.

The study also illustrates the value of embedding mechanistic questions within large mortality trials. Because CHAT already collected MUAC and weight measurements at six-month intervals across nearly three hundred communities, the researchers could test the nutritional hypothesis with statistical power that no standalone study of this size could easily achieve, while respecting the cluster randomized design that guards against contamination between intervention and comparison groups. The trial was registered as NCT03676764 on ClinicalTrials.gov, and the analysis protocol was specified in advance as a secondary objective, reducing the risk of post hoc interpretation. As mass azithromycin programs move from trials toward policy in high-mortality settings, studies like this one will be essential for calibrating expectations, ensuring that a genuinely promising mortality intervention is deployed for what it does, and not credited with benefits the evidence does not support.

Subject of Research: Effects of twice-yearly mass azithromycin distribution on nutritional status in young children

Article Title: Mass azithromycin distribution and nutritional status among children aged 1–59 months: A secondary analysis of a cluster randomized trial

Article References: Ouattara, M., Hu, H., Bountogo, M., Coulibaly, B., Boudo, V., Compaoré, G., Dah, C., Lebas, E., O’Brien, K. S., Arnold, B. F., Lietman, T. M., Sié, A., & Oldenburg, C. E. (2026). Mass azithromycin distribution and nutritional status among children aged 1–59 months: A secondary analysis of a cluster randomized trial. PLOS Global Public Health, 6(10), e0007473. https://doi.org/10.1371/journal.pgph.0007473

Image Credits: AI Generated

DOI: 10.1371/journal.pgph.0007473

Keywords: azithromycin, child mortality, malnutrition, MUAC, weight-for-age Z-score, Burkina Faso, cluster randomized trial, mass drug administration, global health, undernutrition, CHAT trial, PLOS Global Public Health

Scrub typhus is caused by Orientia tsutsugamushi, an obligate intracellular bacterium transmitted by the larvae of trombiculid mites, commonly called chiggers. The disease is endemic across a vast swath of the Asia-Pacific region, stretching from Japan and Korea to northern Australia and from the Indian subcontinent to the Pacific islands, an area that puts an estimated one billion people at risk and produces roughly one million cases each year. Once the bacterium enters the body, it triggers a systemic vasculitis marked by inflammation around blood vessels, dysfunction of the endothelial cells that line them, and leakage of fluid from the circulation. About one-third of patients develop organ dysfunction, which can include respiratory failure, shock, kidney or liver impairment, involvement of the central nervous system, and blood abnormalities. Although mild cases generally resolve well, mortality among severe cases with multi-organ failure can reach 24 percent, and historical data from China have reported an overall death rate of 13.8 percent in untreated patients.

The diagnostic trap that the Guangzhou team documents arises because scrub typhus and Kawasaki disease share a strikingly similar clinical face. Kawasaki disease is an acute vasculitis that predominantly strikes children under five years of age, characterized by prolonged fever, rash, conjunctivitis, inflamed lips and mouth, swollen cervical lymph nodes, and changes in the hands and feet. Roughly 20 percent of untreated patients develop coronary artery aneurysms, making Kawasaki disease the leading cause of acquired heart disease in children in developed countries. Its cause remains incompletely understood, but accumulating evidence points to infectious triggers that provoke a dysregulated immune response in genetically susceptible children. Because scrub typhus also produces fever, rash, lymphadenopathy and, as the new study shows, coronary artery involvement, the two conditions can be almost indistinguishable at the bedside, particularly in regions where both circulate.

The retrospective analysis covered seven patients, two boys and five girls, aged 11 months to 8 years, with a median age of 3 years, all admitted between January 2020 and May 2026 and all long-term residents of Guangdong Province. Six of the seven had plausible exposures: two reported mosquito bites and four described outdoor activity in grass or vegetable fields. Illness onset clustered in the warm months, with four cases beginning in June, consistent with the April-to-September epidemic season of scrub typhus in China. Every child presented with fever, with peak temperatures ranging from 39.1 to 42.0 degrees Celsius, and every child had a rash. Crucially, six of the seven displayed the eschar, the painless black necrotic lesion at the site of the chigger bite that is pathognomonic for scrub typhus. Six children also had bilateral cervical lymphadenopathy, five had enlargement of the liver or spleen, and three developed conjunctival injection or red lips during their illness, features that pushed clinicians toward a Kawasaki diagnosis.

Laboratory testing revealed a profound hyperinflammatory state. C-reactive protein was elevated in all seven children, with values from 32 to 147 milligrams per liter, and serum ferritin, a marker of macrophage activation, was strikingly high in all six patients tested, reaching up to 11,705 nanograms per milliliter. Liver enzymes were mildly to moderately elevated and serum albumin was reduced in every patient. In the three children whose immune cells were profiled, CD8-positive cytotoxic T cells were markedly expanded while the CD4-to-CD8 ratio fell to between 0.30 and 0.50, a pattern suggesting a dominant cytotoxic immune response. Bone marrow examination in four patients revealed hemophagocytosis, the engulfing of blood cells by macrophages, a hallmark of the immune activation syndrome hemophagocytic lymphohistiocytosis, which was clinically diagnosed in two of the children. Complications across the cohort were severe: five had pneumonia, three of them severe; three developed respiratory failure; three went into septic shock; and single patients experienced coagulopathy, pulmonary hemorrhage and encephalopathy.

Echocardiography, performed between days 9 and 14 of illness, defined the coronary pathology. Two children had true aneurysms, one of the right coronary artery and one of the left anterior descending artery, defined by a Z-score of 2.5 or greater. Two had coronary dilatation, with Z-scores between 2.0 and 2.5, and three had intimal thickening, an abnormal buildup of the inner vessel lining exceeding age-adjusted limits. All seven children were initially suspected of having Kawasaki disease, and four formally met the diagnostic criteria for complete or incomplete Kawasaki disease. Six received intravenous immunoglobulin at standard doses, mostly 2 grams per kilogram, the mainstay of Kawasaki therapy, and one child remained febrile even after two full courses. Yet every one of the immunoglobulin-treated children failed to respond, with high fevers recurring for days, sometimes accompanied by falling platelet counts.

The therapeutic turning point came only when antimicrobial therapy targeted at scrub typhus was started, between days 9 and 15 of illness. Two older children, aged 6 and 8, received doxycycline for 7 to 10 days, while five received azithromycin, given intravenously or orally, for one to three courses. All seven children, including the one who never received immunoglobulin, defervesced within one to three days of starting the antibiotics, a speed of response that the authors argue is itself diagnostic. Meta-analytic evidence indicates azithromycin is non-inferior to doxycycline for pediatric scrub typhus, and doxycycline use in young children has not been associated with demonstrable dental enamel defects, addressing a long-standing prescribing concern. Hospital stays ranged from 8 to 29 days, four children required intensive care, and supportive measures ranged from mechanical ventilation to transfusions, albumin, fibrinogen replacement and corticosteroids.

Follow-up imaging offered reassurance. Five of the children with available echocardiography showed complete normalization of their coronary arteries within one week to three months. One child with a right coronary aneurysm received three months of the antiplatelet drug clopidogrel until the vessel healed, and remained normal on repeat imaging after the drug was stopped. Another, with a left anterior descending aneurysm, still had residual dilatation and mild intimal thickening at two months. One patient was lost to echocardiographic follow-up, and the authors acknowledge that the long-term cardiovascular outlook for these children remains unknown, a gap they flag alongside the inherent limits of a small, single-center, retrospective series.

The broader significance of the report lies in what it reveals about infection-driven vascular injury. The authors situate their findings within a growing family of Kawasaki-like syndromes triggered by pathogens, from the Kawasaki-like disease seen in adults with advanced HIV to multisystem inflammatory syndrome in children after SARS-CoV-2 infection, both of which demonstrate that immune dysregulation can precipitate coronary vasculitis. A 2014 Taiwanese cohort study found that adults with scrub typhus had a 37 percent increased risk of acute coronary syndrome within a year of infection, hinting that the cardiovascular consequences of the bacterium extend well beyond childhood. The Guangzhou team also underscores the diagnostic bottleneck: the Weil-Felix test, the most widely used assay at their institution, has a reported sensitivity of only about 16 percent, and three of their patients had repeatedly negative results. Because a diagnosis delayed beyond day 8 of illness is associated with increased mortality, the authors recommend early metagenomic next-generation sequencing, which detected the bacterium in two of their patients, for children with suggestive illness who lack an eschar. Their bottom line for clinicians is unambiguous: in any child with coronary artery lesions and a poor response to immunoglobulin, search the skin for a chigger’s calling card, take a careful exposure history, and treat the pathogen, not just the inflammation.

Subject of Research: Coronary artery lesions associated with pediatric scrub typhus infection

Article Title: Coronary artery lesions in pediatrichus scrub typhus: A case series from Guangzhou, China

Article References: Liu, S., Wang, Q., Gong, Y., Li, X., Zeng, F., & Xu, Y. (2026). Coronary artery lesions in pediatrichus scrub typhus: A case series from Guangzhou, China. PLOS Neglected Tropical Diseases, 20(10), e0014784. https://doi.org/10.1371/journal.pntd.0014784

Image Credits: AI Generated

DOI: 10.1371/journal.pntd.0014784

Keywords: scrub typhus, Orientia tsutsugamushi, coronary artery lesions, Kawasaki disease, children, intravenous immunoglobulin, doxycycline, azithromycin, chiggers, Guangzhou, PLOS Neglected Tropical Diseases, vasculitis

The study, led by Masoumeh Beig and co-first author Sara Hajilari, with Khalil Azizian and Ebrahim Kouhsari as equally contributing corresponding authors, followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and included studies published up to 8 February 2026. The team used R software to compute pooled prevalence estimates with 95 percent confidence intervals, quantifying heterogeneity with Cochran’s Q and tau-squared statistics. Their focus was the minimum inhibitory concentration, or MIC, the lowest concentration of an antibiotic that prevents visible bacterial growth. When MICs rise above established breakpoints, an isolate is classified as non-susceptible, signaling that standard dosing may fail at the site of infection.

Macrolides work by binding to the 50S subunit of the bacterial ribosome, blocking the exit tunnel through which newly synthesized proteins must pass. Erythromycin, the prototype 14-membered macrolide, azithromycin, a 15-membered derivative prized for its tissue penetration, and clarithromycin and roxithromycin, both 14-membered agents, all share this target. Josamycin, a 16-membered macrolide, binds somewhat differently and has retained activity where its smaller relatives have faltered. Resistance in mycoplasmas typically arises through point mutations in the 23S ribosomal RNA gene, particularly in domain V, which alter the drug-binding pocket. Because these organisms lack a cell wall, beta-lactam antibiotics such as penicillins are useless against them, leaving macrolides, tetracyclines, and fluoroquinolones as the principal therapeutic options.

The numbers assembled by the Iranian team paint a genus-specific picture. For Ureaplasma species, pooled non-susceptibility was 13.3 percent for erythromycin, 15.3 percent for roxithromycin, 9.9 percent for clarithromycin, 6.4 percent for azithromycin, and just 2.6 percent for josamycin. For Mycoplasma species, the corresponding estimates were dramatically higher: 63.4 percent for roxithromycin, 84.5 percent for clarithromycin, 78.8 percent for azithromycin, and 7.7 percent for josamycin. Erythromycin non-susceptibility in Mycoplasma reached 75.7 percent. The authors caution, however, that Mycoplasma hominis is intrinsically resistant to 14- and 15-membered macrolides, meaning pooled estimates for erythromycin, azithromycin, clarithromycin, and roxithromycin in that species reflect biology as much as acquired resistance. For M. hominis, the clinically meaningful figure is josamycin, where pooled non-susceptibility was only 6.1 percent.

Geography emerged as a significant modifier for four of the five drugs examined. The meta-analysis detected significant geographic variation in non-susceptibility for erythromycin, clarithromycin, azithromycin, and josamycin, all with P values below 0.05, while roxithromycin showed no significant regional difference, with a P value of 0.283. This pattern suggests that local prescribing habits, population structure, and transmission dynamics shape resistance profiles unevenly across the globe. In regions where azithromycin has been deployed widely, including mass drug administration campaigns and routine sexually transmitted infection management, elevated MICs appear more frequently, whereas areas with lighter macrolide pressure retain comparatively vulnerable bacterial populations.

Perhaps the most reassuring finding is what the analysis did not show. Across the entire dataset, no significant temporal trends were observed for any of the evaluated macrolides: the P value was 0.994 for erythromycin, 0.165 for roxithromycin, 0.615 for clarithromycin, 0.326 for azithromycin, and 0.467 for josamycin. In other words, resistance levels appear to have remained roughly stable over the period covered by the included studies rather than climbing year over year. The authors interpret this cautiously, noting that stability is not the same as safety. A plateau at 75 percent erythromycin non-susceptibility in Mycoplasma offers little therapeutic comfort, and the absence of a trend may simply reflect the coarse resolution of pooled cross-sectional data.

The clinical implications are direct. Urogenital mycoplasmas and ureaplasmas are associated with urethritis, cervicitis, pelvic inflammatory disease, adverse pregnancy outcomes, and complications in neonates, and they are among the most difficult sexually associated bacteria to culture, often requiring nucleic acid amplification tests for detection and specialized broth-based systems for susceptibility testing. When macrolides fail, clinicians typically turn to tetracyclines such as doxycycline or to fluoroquinolones, but resistance to those classes has also been documented in these organisms, narrowing the armamentarium further. The new pooled estimates give guideline committees a quantitative baseline for deciding when macrolide therapy remains defensible and when an alternative should be the default.

Josamycin stands out as the quiet winner of the analysis. With pooled non-susceptibility of 2.6 percent in Ureaplasma and 7.7 percent in Mycoplasma overall, and 6.1 percent in M. hominis specifically, the 16-membered macrolide demonstrated consistently low MICs across the included studies. The authors suggest it may represent a promising alternative, particularly where 14- and 15-membered agents have lost efficacy. Josamycin is not licensed in every country, and its availability varies widely, but the data provide an evidence-based argument for reconsidering its place in treatment algorithms for urogenital infections, especially in regions where azithromycin MICs have drifted upward.

For erythromycin and azithromycin, the message is restraint. The combination of high erythromycin resistance and moderate elevation of azithromycin MICs, the authors conclude, warrants cautious use of these agents, reserving them for cases where susceptibility has been confirmed or where no better option exists. Empirical macrolide monotherapy for suspected Mycoplasma-driven disease, once a reflexive choice, now carries a substantial probability of failure in many settings. The researchers emphasize that ongoing global surveillance remains essential to support evidence-based treatment guidelines, since resistance in organisms with rapid replication and frequent horizontal gene exchange can shift within years, and the fragmented geographic data they aggregated highlight how little standardized susceptibility testing exists in much of the world.

The study, published open access on 8 October 2026 and citable under DOI 10.1186/s12879-026-14585-9, was approved by the Ethics Committee of Golestan University of Medical Sciences and conducted in accordance with the Declaration of Helsinki. The authors declared no competing interests and no external funding, and they state that a language-model tool was used solely to polish the manuscript’s prose, not to collect or analyze data. As antimicrobial resistance continues to erode the utility of first-line antibiotics across the infectious disease spectrum, this meta-analysis offers both a warning and a waypoint: the macrolide era for urogenital Mycoplasma is largely over in much of the world, but for Ureaplasma, and for josamycin across both genera, carefully stewarded options remain.

Subject of Research: Global macrolide antibiotic resistance in urogenital Ureaplasma and Mycoplasma species

Article Title: Global macrolide non-susceptibility in urogenital Ureaplasma and Mycoplasma: a systematic review and meta-analysis

Article References: Beig, M., Azizian, K., Hajilari, S., Shakourzadeh, M. Z., & Kouhsari, E. (2026). Global macrolide non-susceptibility in urogenital Ureaplasma and Mycoplasma: a systematic review and meta-analysis. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14585-9

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14585-9

Keywords: antimicrobial resistance, macrolides, Ureaplasma, Mycoplasma, erythromycin, azithromycin, josamycin, minimum inhibitory concentration, systematic review, meta-analysis, sexually transmitted infections, BMC Infectious Diseases

The condition in question, post-inflammatory wheezing, is a common and troubling sequel of acute pulmonary infection in young children. After an episode of severe pneumonia, many children continue to wheeze for weeks or months, a sign of persistent airway inflammation and dysfunction that can presage recurrent wheezing disorders and, in some children, the later development of asthma. Existing management is largely symptomatic, and the researchers behind the new study emphasize in their impact statement that there is currently no effective treatment specifically for post-inflammatory wheezing. Understanding why the airway stays inflamed after the initial infection has cleared is therefore a pressing question in pediatric respiratory medicine.

To address it, the team enrolled 239 children who had been hospitalized with severe pneumonia and divided them into two groups: those who went on to develop post-inflammatory wheezing and those who did not. The children with wheezing were then assigned to receive either routine symptomatic treatment alone or routine treatment plus a five-day course of azithromycin at a dose of 10 milligrams per kilogram of body weight per day. The researchers compared clinical outcomes between the groups and also examined cellular and molecular markers in bronchoalveolar lavage fluid, the liquid retrieved from the deep airways during fiberoptic bronchoscopy, which provides a direct window into the immunology of the lung.

The comparison revealed a distinctive inflammatory signature in the wheezing children. Their lavage fluid showed an abnormal cellular composition, elevated levels of the pro-inflammatory signaling molecule interleukin-6, and reduced levels of the anti-inflammatory cytokine interleukin-10, a pattern indicating that the immune balance of the airway had tipped toward attack rather than resolution. Crucially, the researchers also found significantly increased expression of SETD1B, a member of the SET domain family of histone methyltransferases, along with elevated levels of H3K4me3, the trimethylated form of histone H3 lysine 4 that SETD1B deposits. Histone modifications such as this one regulate which genes are accessible for transcription, meaning that the wheezing children’s airway immune cells appeared to be carrying an epigenetic imprint that kept inflammatory programs switched on.

When the children received azithromycin on top of routine care, the clinical benefits were clear. The drug shortened the duration of wheezing, reduced the length of hospital stay, and lowered medical costs compared with symptomatic treatment alone. Perhaps the most revealing result, however, came from a subgroup analysis. The researchers found no significant difference in clinical efficacy between children who tested positive for Mycoplasma pneumoniae, a bacterium that azithromycin can kill, and those who tested negative. If the drug were working purely as an antibiotic, mycoplasma-negative children should have derived little benefit. Instead, the benefit was equivalent in both groups, confirming that azithromycin’s therapeutic effect in post-inflammatory wheezing is independent of its anti-mycoplasma activity and must arise from some other property of the molecule.

That other property, the study suggests, is immunomodulation acting through the epigenetic machinery. Macrolide antibiotics like azithromycin have long been known to exert anti-inflammatory effects beyond their antimicrobial role, an observation that has fueled their use in chronic inflammatory airway diseases such as cystic fibrosis, diffuse panbronchiolitis, and chronic obstructive pulmonary disease, and that prompted intense interest in the drug during the COVID-19 pandemic. But the specific molecular targets of this immunomodulation have remained only partially mapped. The new work connects the drug to a precise epigenetic axis, and it builds on the same group’s earlier finding that azithromycin can attenuate wheezing by inhibiting a different histone mark, H3K27me3, mediated by the enzyme EZH2, suggesting that the drug’s anti-inflammatory reach extends across multiple histone methylation systems.

To test the mechanism directly, the researchers turned to an in vitro model. They exposed rat alveolar macrophages, the resident immune cells of the lung’s air sacs, to lipopolysaccharide, a bacterial molecule that reliably triggers a strong inflammatory response. The LPS challenge induced hypermethylation of H3K4me3 driven by SETD1B, disturbed the production of inflammatory cytokines, and pushed the macrophages toward the M1 polarization state, the classically activated, pro-inflammatory phenotype that floods tissue with cytokines. Macrophage polarization, the process by which these cells shift between the inflammatory M1 state and the tissue-repairing M2 state, is increasingly recognized as a central player in inflammatory lung disease, and an excess of M1 polarization is a plausible driver of the persistent airway inflammation seen in wheezing children.

The decisive experiment involved comparing azithromycin with WDR5-0103, a small-molecule inhibitor that specifically blocks SETD1B function. When the LPS-stimulated macrophages were treated with either azithromycin or WDR5-0103 alone, the drug and the inhibitor each significantly reversed the full spectrum of LPS-induced abnormalities: the SETD1B-driven H3K4me3 hypermethylation, the cytokine imbalance, and the M1-skewed polarization. When the two were combined, however, no additional benefit emerged. This lack of synergy is mechanistically telling. If azithromycin and the SETD1B inhibitor were acting through separate pathways, combining them should have produced an additive effect. The absence of one indicates that the two interventions converge on the same target, placing SETD1B-mediated H3K4me3 methylation squarely on the pathway through which azithromycin exerts its anti-inflammatory effect in these cells.

Taken together, the clinical and laboratory findings sketch a coherent causal chain. Severe pulmonary infection elevates SETD1B expression in airway immune cells, which trims excess H3K4me3 marks onto histones near inflammatory genes, keeping them in a transcriptionally active state. This epigenetic drift biases alveolar macrophages toward the M1 phenotype, sustains high interleukin-6 output, suppresses interleukin-10, and maintains the airway in a state of chronic low-grade inflammation that manifests as wheezing. Azithromycin interrupts this chain at its epigenetic root, restoring the M1/M2 balance, normalizing the cytokine milieu, and allowing the airway inflammation to resolve, with the clinical result that children wheeze for less time and leave the hospital sooner.

The implications extend beyond a single drug and a single disease. The study demonstrates that a familiar, inexpensive, and well-characterized antibiotic can be repurposed as an epigenetic modulator for a pediatric condition with no current targeted treatment, and it identifies SETD1B and H3K4me3 as potential biomarkers for identifying which children with post-infectious wheezing carry an active epigenetic inflammatory program. It also raises questions that future work will need to answer, including whether the epigenetic changes seen in lavage fluid predict long-term asthma risk and whether shorter or longer azithromycin regimens might optimize the immunomodulatory effect while minimizing concerns about antibiotic resistance. For now, the study provides the strongest mechanistic account yet of why a five-day course of azithromycin can quiet a child’s wheezing long after the infection that started it has been cleared, and it suggests that the key to treating some chronic airway inflammation lies not in fighting microbes but in editing the inflammatory memory that immune cells carry within their chromosomes.

Subject of Research: Epigenetic and immunomodulatory mechanisms of azithromycin in pediatric post-inflammatory wheezing

Article Title: Azithromycin alleviates post-inflammatory wheezing in children by inhibiting SETD1B-mediated histone H3K4me3 methylation and macrophage polarization

Article References: Wang, L., Peng, C., Wu, S., Tang, T., Lin, Q., & Qin, H. (2026). Azithromycin alleviates post-inflammatory wheezing in children by inhibiting SETD1B-mediated histone H3K4me3 methylation and macrophage polarization. Pediatric Research. https://doi.org/10.1038/s41390-026-05444-z

Image Credits: AI Generated

DOI: 10.1038/s41390-026-05444-z

Keywords: azithromycin, post-inflammatory wheezing, SETD1B, H3K4me3, histone methylation, macrophage polarization, alveolar macrophages, interleukin-6, interleukin-10, pediatric pneumonia, epigenetics, immunomodulation

The research, conducted by a team at Jilin Jianzhu University’s Key Laboratory of Songliao Aquatic Environment and published in Environmental Monitoring and Assessment, is one of the most seasonally resolved portraits yet of antibiotic pollution in a cold-region urban water system. Between July 2024 and April 2025, the investigators sampled three weekdays in each of the four seasons, collecting water from the influents and final effluents of two wastewater treatment plants as well as from sites upstream and downstream of their shared receiving river. The design allowed them to follow the same molecules from the sewer, through the treatment train, and into the aquatic environment across an entire annual cycle.

The analytical workflow was deliberately rigorous. Antibiotics were extracted from water samples using solid-phase extraction, a technique that concentrates trace organic compounds onto a sorbent cartridge before they are eluted for analysis. Quantification was then performed by ultra-high-performance liquid chromatography coupled with tandem mass spectrometry, an approach sensitive enough to detect individual pharmaceutical compounds at concentrations of nanograms per liter, equivalent to parts per trillion. This combination of concentration and detection methods is now the standard for pharmaceutical monitoring, because the environmental levels involved are far too low for conventional chemical assays yet high enough to exert biological effects on microorganisms.

What the measurements revealed was a steep concentration gradient across the urban water cycle. In the raw sewage entering the plants, antibiotic concentrations ranged from undetectable to a remarkable 2,873.03 nanograms per liter. After treatment, effluent concentrations fell to between not detected and 941.59 nanograms per liter, and in the receiving river itself the measured levels ranged from not detected up to 93.25 nanograms per liter. Two chemical families dominated the profile: the fluoroquinolones, a class of broad-spectrum synthetic antibiotics that includes drugs such as ciprofloxacin and norfloxacin, and the macrolides, which include azithromycin and roxithromycin. Both classes are heavily prescribed in China and are known to persist in aquatic environments because they resist both biodegradation and sunlight-driven photolysis.

The seasonal signal was unmistakable. Concentrations were generally higher in winter and lower in summer, a pattern the authors link to several interacting factors. In cold climates, winter brings higher rates of respiratory infection and correspondingly greater antibiotic consumption, which flushes more of these compounds into the sewer system. At the same time, the biological processes inside treatment plants slow down dramatically as temperatures drop, because the microbial communities that break down organic pollutants, including pharmaceuticals, become far less active in cold wastewater. Reduced dilution in frozen, low-flow rivers compounds the problem, since the same mass of discharged antibiotic ends up in a smaller volume of receiving water.

Treatment performance told the same seasonal story from the other direction. For the eight antibiotics that were consistently detected, the apparent overall removal efficiency across the plants ranged from 32.99 percent to complete elimination, but removal was generally lower in winter and spring. This matters because conventional activated-sludge treatment was never designed with pharmaceuticals in mind. Antibiotics leave wastewater plants through three main pathways: biodegradation by the microbial community, sorption onto sludge particles that are settled out of the water, and abiotic processes such as hydrolysis. When water temperatures fall, all three mechanisms weaken, and a larger fraction of the incoming drug load simply passes through the plant and into the river.

One of the most practically interesting findings concerns the comparison between treatment technologies. The two plants in the study operated three distinct treatment lines: a conventional anaerobic-anoxic-oxic configuration followed by clarification, filtration, and ozonation; a similar biological process followed by clarification, cloth-media filtration, and ultraviolet disinfection; and an integrated anaerobic-anoxic-oxic membrane bioreactor, in which fine membranes replace secondary clarifiers and allow a much higher concentration of slow-growing microorganisms to be maintained in the bioreactor. During winter, the membrane bioreactor line achieved comparatively higher apparent removal of the macrolides azithromycin and roxithromycin than the parallel conventional line. The likely explanation lies in the longer solids retention times and denser microbial populations that membrane systems sustain, giving cold-slowed bacteria more opportunity and more biomass to degrade or sorb these persistent compounds even when conditions are unfavorable.

Downstream of the outfalls, the river told a coherent spatial story as well. Antibiotic concentrations rose sharply near the discharge points and then generally declined with distance downstream, as dilution, sedimentation, photodegradation, and microbial breakdown gradually whittled away the effluent signal. In a cold-region river, however, this natural attenuation is weakened for much of the year. Ice cover reduces light penetration and suppresses photolysis, low winter flows reduce dilution capacity, and cold water slows biodegradation, so the plume of pharmaceuticals extends further and persists longer than it would in a warmer climate. This is why the study’s cold-region focus is significant: most antibiotic monitoring data come from temperate or tropical systems, and the winter dynamics of northern cities have been comparatively understudied.

The ecological risk assessment converted concentration data into a measure of biological concern using risk quotients, a screening approach that compares measured environmental concentrations with predicted no-effect concentrations derived from ecotoxicological studies. The verdict was pointed: azithromycin was the main contributor to ecological risk, reaching moderate to high risk levels in winter. This finding resonates with a growing body of international research showing that macrolides are among the most hazardous antibiotics in surface waters, partly because they are toxic to photosynthetic aquatic organisms such as algae and cyanobacteria, the foundation of aquatic food webs. Even more troubling is the resistance dimension. Laboratory studies have demonstrated that bacteria can be selected for antibiotic resistance at concentrations far below those that cause obvious toxicity, meaning that chronic exposure to even nanogram-per-liter levels in a river can act as a subtle evolutionary engine, enriching resistant strains and the genes that carry resistance.

The Changchun study arrives amid intensifying global concern about antimicrobial resistance, which the World Health Organization ranks among the top public health threats of the century. Wastewater treatment plants occupy a pivotal position in this problem: they concentrate antibiotics, resistant bacteria, and resistance genes from entire urban populations into a single discharge stream, and they are simultaneously one of the few practical points of intervention. The findings from Northeast China suggest that cold-climate cities may need seasonally adjusted strategies, from enhanced winter treatment capacity to technologies such as ozonation and membrane bioreactors that maintain performance when conventional biology falters. They also underscore the value of long-term, seasonally resolved monitoring, because a snapshot taken in summer would have dramatically underestimated both the concentrations and the risks that northern rivers actually face. As winters in many regions grow more variable and urban pharmaceutical use continues to rise, the frozen rivers of places like Changchun may offer an early warning of challenges that colder cities worldwide have only begun to confront.

Subject of Research: Seasonal occurrence, treatment removal, and ecological risk of antibiotics in municipal wastewater and a receiving river in a cold-region Chinese city

Article Title: Seasonal patterns and ecological risks of antibiotics in municipal wastewater treatment plants and a receiving river in Northeast China

Article References: Sun, K., Meng, Q., Zhang, C., Wen, Z., Zhu, X., Li, R., Wang, Y., & Wang, M. (2026). Seasonal patterns and ecological risks of antibiotics in municipal wastewater treatment plants and a receiving river in Northeast China. Environmental Monitoring and Assessment, 198(11), Article 1144. https://doi.org/10.1007/s10661-026-16003-8

Image Credits: AI Generated

DOI: 10.1007/s10661-026-16003-8

Keywords: antibiotics, wastewater treatment plants, receiving river, seasonal variation, azithromycin, macrolides, fluoroquinolones, membrane bioreactor, ecological risk, antimicrobial resistance, Northeast China, cold-region water quality

The science underlying the disease is elegantly captured by what researchers call the vicious vortex, a conceptual framework building on the vicious cycle theory first proposed by Professor Peter Cole in 1986. Four interrelated factors drive the pathology: airway inflammation, impaired mucociliary clearance, airway infection, and structural lung damage. Each element feeds the others, so that infection triggers inflammation, inflammation impairs the tiny hair-like cilia that sweep mucus from the airways, stagnant secretions harbor more bacteria, and the resulting damage further distorts the airway architecture. Exacerbations accelerate this vortex. They are formally defined as a deterioration in three or more key symptoms lasting at least 48 hours, including cough, sputum volume or purulence, breathlessness, fatigue, or coughing up blood, alongside a clinician’s judgment that treatment must change. Each episode is associated with declining lung function, diminished quality of life, and increased mortality, and a history of exacerbations is itself a major predictor of future ones.

The patient at the heart of the case study illustrates just how formidable this vortex can become. Diagnosed with bronchiectasis in 2005 at age 55, he also carries diagnoses of asthma and chronic obstructive pulmonary disease, and he is an ex-smoker with 20 pack-years of history. Serial CT scans reveal extensive bilateral bronchiectasis concentrated in the mid and lower zones of his lungs, and his Bronchiectasis Severity Index score of 18 places him in a high-risk category. He suffers numerous exacerbations every year, driven by the combined burden of all three chronic lung conditions. In July 2024, he noticed the familiar warning signs: coughing up large amounts of purulent sputum, worsening breathlessness, and crushing exhaustion. Recognizing an exacerbation, he did exactly what his self-management plan advised, starting a two-week course of oral co-amoxiclav from a rescue pack kept at home and provided by his general practitioner.

That early self-treatment, which the new ERS guidelines explicitly endorse, proved insufficient. When he failed to improve, his GP prescribed a further two weeks of the same antibiotic, and still his symptoms persisted. Only when he contacted his specialist hospital team was his care escalated, and here the case illuminates a crucial structural innovation in modern British healthcare: the respiratory virtual ward. Admitted to this hospital-at-home service, the patient received close monitoring from a multidisciplinary team along with hospital-level diagnostics and interventions, including the ability to self-administer intravenous treatments in his own home. The NHS launched a national virtual wards programme in 2023 aiming to expand exactly this kind of hospital-level care at home, and evidence suggests patients often prefer it, feeling more comfortable and recovering faster in familiar surroundings while health systems relieve pressure on physical beds.

The microbiology that followed reads like a detective story. Consistent with guideline recommendations, a sputum sample had been taken at the onset of the exacerbation before antibiotics began, and it grew Proteus mirabilis, a bacterium not typically associated with bronchiectasis, sensitive to co-amoxiclav, along with Candida species, which are common commensals that usually require no targeted therapy. When oral antibiotics failed, the team switched to intravenous meropenem, one gram three times daily, self-administered at home for two weeks. Research on home intravenous therapy in bronchiectasis remains limited, but retrospective studies in adults and children suggest clinical outcomes comparable to inpatient care, with the added benefits of reduced risk of hospital-acquired infection and better quality of life. Remarkably, even intravenous meropenem failed to produce improvement, and the authors of the case report argue that the problem was likely not antimicrobial resistance but inadequate airway clearance, a reminder that antibiotics alone cannot break the vicious vortex if secretions remain trapped in damaged airways.

This is where the guidelines place enormous weight on airway clearance techniques, or ACTs, such as active cycle of breathing techniques and positive expiratory pressure devices. These interventions directly target the impaired mucociliary clearance component of the vortex, improving sputum clearance, reducing the burden of cough, lowering exacerbation risk, and improving quality of life. The ERS recommends that ACTs be adapted in frequency, intensity, and technique during exacerbations, and the patient was duly referred to physiotherapy. Yet he waited several months to see a respiratory physiotherapist, a delay the authors describe as sadly reflective of real-life disparities in access across the UK. When he finally received instruction, his first device, a positive expiratory pressure mouthpiece, proved intolerable because it triggered coughing, so he was switched to an oscillating positive expiratory pressure device with a slow expiratory phase to suppress the cough reflex, used after his COPD inhaler to open the airways first. At his six-week follow-up he reported easier clearance and thinner mucus, a small technical adjustment with a meaningful clinical payoff.

The bacterial saga continued. Two weeks after discharge he was readmitted with persistently high sputum volume, and cultures now showed a heavy growth of Pseudomonas aeruginosa, a notoriously resilient pathogen in bronchiectasis. The guidelines recommend eradication treatment for any new isolation of this organism, typically two weeks of oral or intravenous antibiotics followed by six to twelve weeks of inhaled antibiotics. The patient received two weeks of home intravenous meropenem, extended by two more weeks, plus daily hospital visits for intravenous tobramycin at three milligrams per kilogram, later escalated to five after monitoring confirmed stable kidney function. Evidence for dual antimicrobial therapy against Pseudomonas in bronchiectasis is thin, but data from cystic fibrosis populations support combining a beta-lactam with an aminoglycoside for chronic infection, always balanced against the risks of kidney and ear toxicity in older patients. By December 2024, bronchoscopy revealed Pseudomonas resistant to tobramycin, colistin, and gentamicin, confirming the eradication attempt had failed, and his treatment moved to three weeks of intravenous ceftazidime at home.

With chronic Pseudomonas infection now established, the guidelines strongly recommend long-term inhaled antibiotics, and the patient’s nebulised tobramycin prophylaxis was escalated from alternating months to continuous therapy. The guidelines also strongly recommend long-term macrolides for patients at high risk of exacerbations despite standard care, and large randomized trials such as EMBRACE and BAT have demonstrated that daily azithromycin reduces exacerbation frequency, including in patients with chronic Pseudomonas. He began 500 milligrams three times weekly, but only after screening for nontuberculous mycobacterial infection, QTc prolongation on his heart rhythm tracing, and liver and kidney abnormalities, as both the ERS and British Thoracic Society guidelines demand, with repeat checks four weeks later. He has tolerated the regimen well and remains stable, with no antibiotics needed for bronchiectasis exacerbations since March 2025 and a culture-negative sputum sample in April 2025.

The case also exposes the harder edges of long-term management. Mucoactive drugs such as hypertonic saline and carbocisteine are recommended when airway clearance alone fails to control symptoms, though a recent trial found neither significantly reduced exacerbation rates, and the patient’s own experience was mixed: years of nebulised normal saline with no evidence base, a trial of seven percent hypertonic saline that only slightly thinned his sputum, and a final refusal to restart it because the treatment burden was too great. He declined further pulmonary rehabilitation despite guideline support, and his long-term inhaled corticosteroids, discouraged for bronchiectasis itself, are appropriately continued for his asthma and COPD. His vaccination record, covering influenza, COVID-19, pneumococcal disease, respiratory syncytial virus, and shingles, exemplifies the preventive backbone the guidelines demand. The authors conclude that the new ERS guidance gives health services a benchmark for improving care, and perhaps most importantly, a lever to argue for faster access to the respiratory physiotherapy that this case shows can matter as much as any antibiotic.

Subject of Research: Real-world management of difficult bronchiectasis exacerbations guided by the 2025 European Respiratory Society guidelines

Article Title: Real‐World Management of Difficult Exacerbations of Bronchiectasis: A Case Study to Illustrate How Guidelines Can Support Best Practice

Article References: Bianca, H., Toby, C., Anand, S., & Paul, M. (2026). Real‐World Management of Difficult Exacerbations of Bronchiectasis: A Case Study to Illustrate How Guidelines Can Support Best Practice. Clinical Case Reports, 14(10), Article e73566. https://doi.org/10.1002/ccr3.73566

Image Credits: AI Generated

DOI: 10.1002/ccr3.73566

Keywords: bronchiectasis, exacerbations, ERS guidelines, Pseudomonas aeruginosa, airway clearance techniques, virtual ward, antibiotics, azithromycin, respiratory physiotherapy, mucociliary clearance, inhaled antibiotics, pulmonary rehabilitation