Surveillance of antimicrobial resistance (AMR) in non-typhoidal Salmonella enterica (NTS), is essential for monitoring transmission of resistance from the food chain to humans, and for establishing effective treatment protocols. We evaluated the prediction of phenotypic resistance in NTS from genotypic profiles derived from whole genome sequencing (WGS). Genes and chromosomal mutations responsible for phenotypic resistance were sought in WGS data from 3,491 NTS isolates received by Public Health England’s Gastrointestinal Bacteria Reference Unit between April 2014 and March 2015. Inferred genotypic AMR profiles were compared with phenotypic susceptibilities determined for fifteen antimicrobials using EUCAST guidelines. Discrepancies between phenotypic and genotypic profiles for one or more antimicrobials were detected for 76 isolates (2.18%) although only 88/52,365 (0.17%) isolate/antimicrobial combinations were discordant. Of the discrepant results, the largest number were associated with streptomycin (67.05%, n = 59). Pan-susceptibility was observed in 2,190 isolates (62.73%). Overall, resistance to tetracyclines was most common (26.27% of isolates, n = 917) followed by sulphonamides (23.72%, n = 828) and ampicillin (21.43%, n = 748). Multidrug resistance (MDR), i.e., resistance to three or more antimicrobial classes, was detected in 848 isolates (24.29%) with resistance to ampicillin, streptomycin, sulphonamides and tetracyclines being the most common MDR profile (n = 231; 27.24%). For isolates with this profile, all but one were S. Typhimurium and 94.81% (n = 219) had the resistance determinants blaTEM-1, strA-strB, sul2 and tet(A). Extended-spectrum β-lactamase genes were identified in 41 isolates (1.17%) and multiple mutations in chromosomal genes associated with ciprofloxacin resistance in 82 isolates (2.35%). This study showed that WGS is suitable as a rapid means of determining AMR patterns of NTS for public health surveillance.

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Salmonella enterica subsp. enterica serovar Typhimurium is a common cause of enterocolitis in humans globally, with multidrug resistant (MDR) strains posing an enhanced threat. S. Typhimurium is also a pathogen in food-production animals, and these populations can act as reservoirs of the bacterium. Therefore, surveillance and control measures within food-production animal populations are of importance both to animal and human health and have the potential to be enhanced though improved understanding of the epidemiology of S. Typhimurium within and between food-production animal populations. Here, data from Scotland and national surveillance England and Wales data for isolates from cattle ( n = 1115), chickens ( n = 248) and pigs ( n = 2174) collected between 2003 and 2014 were analyzed. Ecological diversity analyses and rarefaction curves were used to compare the diversity of observed antimicrobial resistance (AMR) profiles between the host species, and within host species populations. Higher AMR profile diversity was observed in isolates from pigs compared to chickens across diversity measures and isolates from cattle for three of four diversity measures. Variation in AMR profile diversity between production sectors was noted, with higher AMR diversity of isolates from broiler compared to layer chickens, breeder compared to rearer and finisher pigs and beef compared to dairy cattle. Findings indicate variation in AMR profile diversity both within and between food-production animal host species. These observations suggest alternate sources of AMR bacteria and/or variation in selective evolutionary pressures within and between food-production animal host species populations.

Highly pathogenic avian influenza (HPAI) H5N1 virus has been circulating in Vietnam since 2003, whilst outbreaks of HPAI H5N6 virus are more recent, having only been reported since 2014. Although the spatial distribution of H5N1 outbreaks and risk factors for virus occurrence has been extensively studied, there have been no comparative studies for H5N6. Data collected through active surveillance of Vietnamese live bird markets (LBMs) between 2011 and 2015 were used to explore and compare the spatiotemporal distributions of H5N1- and H5N6-positive LBMs. Conditional autoregressive models were developed to quantify spatiotemporal associations between agroecological factors and the two HPAI strains using the same set of predictor variables. Unlike H5N1, which exhibited a strong north–south divide, with repeated occurrence in the extreme south of a cluster of high-risk provinces, H5N6 was homogeneously distributed throughout Vietnam. Similarly, different agroecological factors were associated with each strain. Sample collection in the months of January and February and higher average maximum temperature were associated with higher likelihood of H5N1-positive market-day status. The likelihood of market days being positive for H5N6 increased with decreased river density, and with successive Rounds of data collection. This study highlights marked differences in spatial patterns and risk factors for H5N1 and H5N6 in Vietnam, suggesting the need for tailored surveillance and control approaches.

SummaryBackgroundPneumococcal Conjugate Vaccine (PCV) which targets up to 13 serotypes of Streptococcus pneumoniae is very effective at reducing disease in young children; however, rapid increases in replacement with non-PCV serotypes remains a concern. Serotype 24F is one of the major invasive serotypes that mediates serotype replacement in France and multiple other countries. We aimed to identify the major pneumococcal lineage that has driven the increase of serotype 24F in France, and provide context for the findings by investigating the global diversity of serotype 24F pneumococci and characterise the driver lineage from a global perspective and elucidate its spatiotemporal transmission in France and across the world.MethodsWe whole-genome sequenced a collection of 419 serotype 24F S. pneumoniae from asymptomatic carriers and invasive disease cases among individuals <18 years old in France between 2003 and 2018. Genomes were clustered into Global Pneumococcal Sequence Clusters (GPSCs) and clonal complexes (CCs) so as to identify the lineages that drove the increase in serotype 24F in France. For each serotype 24F lineage, we evaluated the invasive disease potential and propensity to cause meningitis by comparing the proportion of invasive disease cases with that of carriers. To provide a global context of serotype 24F and the driver lineage, we extracted relevant genomes and metadata from the Global Pneumococcal Sequencing (GPS) project database (n=25,590) and additionally sequenced a collection of 91 pneumococcal isolates belonging to the lineage that were responsible for the serotype 24F increase in Spain during the PCV introduction for comparison. Phylogenetic, evolutionary, and spatiotemporal analysis were conducted to understand the mechanism underlying the global spread of serotype 24F, evolutionary history and long-range transmissions of the driver lineage.FindingsA multidrug-resistant pneumococcal lineage GPSC10 (CC230) drove the serotype 24F increase in both carriage and invasive disease in France after PCV13 introduction. When compared with other serotype 24F lineages, it exhibited a 1.4-fold higher invasive disease potential and 1.6-fold higher propensity to cause meningitis. Globally, serotype 24F was widespread, largely due to clonal dissemination of GPSC10, GPSC16 (CC66) and GPSC206 (CC7701) rather than recent capsular switching. Among these lineages, only GPSC10 was multidrug-resistant. It expressed 17 serotypes, with only 6 included in PCV13 and none of the expected PCVs covered all serotypes expressed by this lineage. Global phylogeny of GPSC10 showed that all serotype 24F isolates except for one were clustered together, regardless of its country of origin. Long-range transmissions of GPSC10-24F from Europe to Israel, Morocco and India were detected. Spatiotemporal analysis revealed that it took ∼5 years for GPSC10- 24F to spread across French provinces. In Spain, we detected that the serotype 24F driver lineage GPSC10 underwent a rapid change of serotype composition from serotype 19A to 24F during the introduction of PCV13 (targets 19A but not 24F), indicating that pre-existence of serotype variants enabled GPSC10 to survive and expand under vaccine-selective pressure.InterpretationOur work further shows the utility of bacterial genome sequencing to better understand the pneumococcal lineages behind the serotype changes and reveals that GPSC10 alone is a challenge for serotype-based vaccine strategy. More systematic investigation to identify lineages like GPSC10 will better inform and improve next-generation preventive strategies against pneumococcal diseases.FundingBill & Melinda Gates Foundation, Wellcome Sanger Institute, and the US Centers for Disease Control.

Plasmids are mobile elements that can carry genes encoding traits of clinical concern, including antimicrobial resistance (AMR) and virulence. Population-level studies of Enterobacterales , including Escherichia coli, Shigella and Klebsiella , indicate that plasmids are important drivers of lineage expansions and dissemination of AMR genes. Salmonella Typhimurium is the second most common cause of salmonellosis in humans and livestock in the UK and Europe. The long-term dynamics of plasmids between S. Typhimurium were investigated using isolates collected through national surveillance of animals in England and Wales over a 25-year period. The population structure of S. Typhimurium and its virulence plasmid (where present) were inferred through phylogenetic analyses using whole-genome sequence data for 496 isolates. Antimicrobial resistance genes and plasmid markers were detected in silico. Phenotypic plasmid characterization, using the Kado and Liu method, was used to confirm the number and size of plasmids. The differences in AMR and plasmids between clades were striking, with livestock clades more likely to carry one or more AMR plasmid and be multi-drug-resistant compared to clades associated with wildlife and companion animals. Multiple small non-AMR plasmids were distributed across clades. However, all hybrid AMR–virulence plasmids and most AMR plasmids were highly clade-associated and persisted over decades, with minimal evidence of horizontal transfer between clades. This contrasts with the role of plasmids in the short-term dissemination of AMR between diverse strains in other Enterobacterales in high-antimicrobial-use settings, with implications for predicting plasmid dissemination amongst S. Typhimurium.

Antimicrobial resistant Salmonella enterica serovar Concord (S. Concord) is known to cause severe gastrointestinal and bloodstream infections in patients from Ethiopia and Ethiopian adoptees, and occasional records exist of S. Concord linked to other countries. The evolution and geographical distribution of S. Concord remained unclear. Here, we provide a genomic overview of the population structure and antimicrobial resistance (AMR) of S. Concord by analysing genomes from 284 historical and contemporary isolates obtained between 1944 and 2022 across the globe. We demonstrate that S. Concord is a polyphyletic serovar distributed among three Salmonella super-lineages. Super-lineage A is composed of eight S. Concord lineages, of which four are associated with multiple countries and low levels of AMR. Other lineages are restricted to Ethiopia and horizontally acquired resistance to most antimicrobials used for treating invasive Salmonella infections in low- and middle-income countries. By reconstructing complete genomes for 10 representative strains, we demonstrate the presence of AMR markers integrated in structurally diverse IncHI2 and IncA/C2 plasmids, and/or the chromosome. Molecular surveillance of pathogens such as S. Concord supports the understanding of AMR and the multi-sector response to the global AMR threat. This study provides a comprehensive baseline data set essential for future molecular surveillance.

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