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In August 2015, Public Health England detected an outbreak of Shiga toxin-producing Escherichia coli (STEC) serotype O157:H7 caused by contaminated salad leaves in a mixed leaf prepacked salad product from a national retailer. The implicated leaves were cultivated at five different farms and the zoonotic source of the outbreak strain was not determined. In March 2016, additional isolates from new cases were identified that shared a recent common ancestor with the outbreak strain. A case–case study involving the cases identified in 2016 revealed that ovine exposures were associated with illness ( n = 16; AOR 8·24; 95% CI 1·55–39·74). By mapping the recent movement of sheep and lambs across the United Kingdom, epidemiological links were established between the cases reporting ovine exposures. Given the close phylogenetic relationship between the outbreak strain and the isolates from cases with ovine exposures, it is plausible that ovine faeces may have contaminated the salad leaves via untreated irrigation water or run-off from fields nearby. Timely and targeted veterinary and environmental sampling should be considered during foodborne outbreaks of STEC, particularly where ready to eat vegetables and salads are implicated.

Urinary tract infections (UTIs) are among the most common bacterial infections worldwide and are primarily caused by Escherichia coli . While E. coli is known to colonize both humans and food-producing animals, the extent to which zoonotic strains impact human disease remains poorly understood. Emerging evidence suggests that food animals may serve as an underrecognized reservoir for extraintestinal pathogenic E. coli (ExPEC). In this study, we used a genomic attribution model to quantify the contribution of zoonotic strains to UTIs in Southern California. We found that approximately 18% of E. coli UTIs were likely attributable to food animals. Individuals living in high-poverty neighborhoods had a 1.6-fold increased risk of zoonotic UTIs compared to those in low-poverty areas. These findings highlight zoonotic transmission as an important driver of UTIs and suggest that reducing ExPEC in food-animal reservoirs could help lower disease burden and address health disparities.

Chronic typhoid fever, caused by persistent Salmonella Typhi infection, remains a significant public health concern in multiple regions throughout the world. There is currently no direct animal model utilizing S . Typhi that has been demonstrated to recapitulate the carrier state of typhoid fever. This lack of an animal model has precluded in vivo studies on the mechanisms of infection unique to this serovar. This study establishes and characterizes a new murine model of chronic S . Typhi carriage and demonstrates its utility with the identification of novel anti-biofilm compounds that disperse S . Typhi biofilms from gallbladder gallstones. This new model will provide a means for further studies into S . Typhi chronic infection.

Antimicrobial resistance (AMR) is one of the most urgent health threats of the 21st century. Surveillance is needed to enable timely interventions, close knowledge gaps, and anticipate long-term trends. Current frameworks rely heavily on clinical data, which often fail to capture population-level dynamics. Wastewater-based surveillance (WBS) offers a complementary approach by detecting antibiotic resistance genes (ARGs) in sewage. In AMR surveillance, early warning includes the detection of novel or clinically relevant ARGs, including those carried by mobile genetic elements (MGEs) before they affect clinical outcomes. WBS can also reveal resistome composition, dissemination routes, and ecological drivers of AMR. This is especially relevant in settings with poor sanitation, high exposure, and limited clinical reporting. Unlocking its potential will require harmonized protocols, sustained investment, and strong ethical measures. Within a One Health framework, WBS can strengthen equitable and evidence-based strategies against AMR.

Antimicrobial resistance (AMR) is a major threat to global health. Understanding the emergence, evolution, and transmission of individual antibiotic resistance genes (ARGs) is essential to develop sustainable strategies combatting this threat. Here, we use metagenomic sequencing to analyse ARGs in 757 sewage samples from 243 cities in 101 countries, collected from 2016 to 2019. We find regional patterns in resistomes, and these differ between subsets corresponding to drug classes and are partly driven by taxonomic variation. The genetic environments of 49 common ARGs are highly diverse, with most common ARGs carried by multiple distinct genomic contexts globally and sometimes on plasmids. Analysis of flanking sequence revealed ARG-specific patterns of dispersal limitation and global transmission. Our data furthermore suggest certain geographies are more prone to transmission events and should receive additional attention. Understanding the emergence, evolution, and transmission of antibiotic resistance genes (ARGs) is essential to combat antimicrobial resistance. Here, Munk et al. analyse ARGs in hundreds of sewage samples from 101 countries and describe regional patterns, diverse genetic environments of common ARGs, and ARG-specific transmission patterns.

Salmonella inhabiting environmental niches, such as water and soil, remain underexplored despite their potential role in pathogen gene pool evolution and infection burden. Using a global data set that includes newly sequenced genomes of isolates from India, we show that environmental populations are active evolutionary reservoirs that maintain a conserved virulence core while rapidly exchanging antimicrobial resistance genes via horizontal gene transfer. The detection of early-stage colistin resistance and multidrug-resistant lineages in global ecosystems identify these environments as potential early-warning systems for emerging clinical threats. Our findings demonstrate that Indian environmental strains of Salmonella are deeply interconnected with global lineages, underscoring the need for global surveillance. Collectively, genomic epidemiology as described herein reinforces a One Health framework and highlights environmental surveillance as a critical requirement in the context of high-risk pathogens such as Salmonella .

Toxoplasmosis is a disease of worldwide distribution, causing high morbidity and mortality in humans, as well as heavily impacting animal health and the economy. Toxoplasma gondii, the causative agent, is an intracellular parasite with a complex life cycle whose completion entails asexual, pre-sexual, and sexual stage conversions. Pre-sexual and sexual differentiation take place only within the intestinal epithelium of felines. Recently, several transcriptional factors and epigenetic components crucial to trigger parasite stage transitions within the cat have been identified, allowing, through precise genetic manipulation, obtaining pre-sexual stages known as merozoites in vitro. Through conditional depletion of two pre-sexual stage-specific gene silencing transcription factors, AP2XII-1 and AP2XII-2, we have characterized the interplay between cell division and the sequence of events leading up to differentiation of tachyzoites into merozoites. We explored genome duplication, assembly of daughter cells, karyokinesis, and cytokinesis, characterizing the differential cell division modes and kinetics undergone by critical structures along the differentiation axis. Building onto the pre-existing body of knowledge, primarily describing the underpinnings of these forms of division by transmission electron microscopy, our work contributes previously unexplored temporal and spatial resolution to the transitions between endodyogeny and endopolygeny, providing a conceptual framework for understanding and exploring T. gondii’s route of sexual differentiation.IMPORTANCESexual development in Toxoplasma gondii is essential for transmission, but remains poorly understood, largely because pre-sexual stages are restricted to the feline intestine and have only recently become experimentally accessible. Here, we leverage an in vitro differentiation system to resolve how parasites transition toward merozoite formation at the cellular level. By combining expansion microscopy, stage-specific markers, and quantitative analyses, we define the temporal sequence of nuclear division and daughter cell assembly during merogony, addressing longstanding ambiguity regarding division modes in these stages. Our findings reveal that parasites can adopt alternative division strategies emerging from a polyploid intermediate, highlighting an unexpected degree of flexibility in how cell division is executed during differentiation. Beyond refining this developmental framework, this work establishes a foundation for future mechanistic studies of pre-sexual biology and provides broader insight into the diversity of eukaryotic cell division strategies.

Bacterial pneumonia can lead to severe cardiovascular complications and is a major contributor to increased mortality among hospitalized patients, either directly or indirectly. Pseudomonas aeruginosa , an opportunistic pathogen frequently encountered in hospital settings, accounts for nearly 20% of all infections in intensive care units (ICUs). Our previous studies demonstrated that P. aeruginosa lung infection induces profound cardiac electrical abnormalities and left ventricular (LV) dysfunction, despite minimal bacterial dissemination to the heart. In the present study, we identify exosomes released from infected host cells and outer membrane vesicles (OMVs) secreted by P. aeruginosa as critical mediators of this cardiac dysfunction. We show that host-derived exosomes are enriched with bacterial OMVs containing toxins and other immunogenic molecules, which promote systemic inflammation and tissue injury, ultimately contributing to cardiac impairment.

Understanding the dynamics between phages and their bacterial hosts is critical for elucidating disease burden; however, their potential for surveillance remains underexplored. To our knowledge, this is the first study that longitudinally investigated major diarrheal pathogens and their phages in both clinical and environmental sources to assess the potential of bacteriophages as a tool to improve diarrheal surveillance. The high frequency of phages compared to the host bacterial counterparts suggests a valuable, yet underutilized, role for phages in surveillance systems. Strong seasonal alignment between V. cholerae O1 and its phages, both peaking in late September, suggests that phage dynamics may reflect pathogen transmission. These preliminary observations raise the possibility that wastewater-derived Vibrio phages could function as early indicators of cholera burden. Future research should aim to explore the complex and poorly understood interactions between phages and their bacterial hosts, particularly how these dynamics shape pathogen populations in endemic settings.

The pressure of the coronavirus disease 2019 (COVID-19) pandemic on global healthcare systems and societies was unprecedented in the modern era. Social restrictions, containment measures, and disruptions in antimicrobial prescriptions and consumption during the pandemic have been reported to alter the epidemiology of bacterial diseases, although these effects likely differed markedly between locations. Here, we compare the clinical, clonal distribution, and genomic features of bloodstream isolates before, during, and after COVID-19 in two hospitals on different continents: Parc Taulí University Hospital (Spain) and Dartmouth-Hitchcock Medical Center (USA). We hypothesize that pandemic-related environmental perturbations, such as those due to infection control practices and antimicrobial exposure, may have contributed to shifts in the diversity of circulating bacterial lineages and genomic elements. Our findings revealed changes in the distribution of low-frequency clones, antimicrobial resistance genes, and virulence factors, potentially reflecting changes in selective pressures in clinical environments.