MOB-suite: software tools for clustering, reconstruction and typing of plasmids from draft assemblies

Genomic insights into the rapid rise of Pseudomonas aeruginosa ST463: A high-risk lineage's adaptive strategy in China

High-risk lineages of Pseudomonas aeruginosa pose a serious threat to public health, causing severe infections with high mortality rates and limited treatment options. The emergence and rapid spread of the high-risk lineage ST463 in China have further exacerbated this issue. However, the basis of its success in China remains unidentified. In this study, we analyzed a comprehensive dataset of ST463 strains from 2000 to 2023 using whole genome sequencing to unravel the epidemiological characteristics, evolutionary trajectory, and antibiotic resistance profiles. Our findings suggest that ST463 likely originated from a single introduction from North America in 2007, followed by widespread domestic dissemination. Since its introduction, the lineage has undergone significant genomic changes, including the acquisition of three unique regions that enhanced its metabolism and adaptability. Frequent recombination events, along with the burden of bacteriophages, antibiotic resistance genes, and the spread of c1-type (blaKPC-2) plasmid-carrying strains, have played crucial roles in its expansion in China. Mutation analysis reveals adaptive responses to antibiotics and selective pressures on key virulence factors, indicating that ST463 is evolving toward a more pathogenic lifestyle.

Integrative and conjugative elements associated with antimicrobial resistance in multidrug resistant Pasteurella multocida isolates from bovine respiratory disease (BRD)-affected animals in Spanish feedlots

The emergence of multidrug-resistance (MDR) in Pasteurella multocida, a major contributor to bovine respiratory disease (BRD) is being increasingly reported, often linked to the carriage of antimicrobial resistance genes (ARGs) on integrative and conjugative elements (ICEs). The resistance phenotype for 19 antimicrobials was determined using broth microdilution in 75 Pasteurella multocida isolates from healthy and BRD-affected cattle from five feedlots. The genomes of 32 isolates were sequenced to identify ARG) and mobile genetic elements (MGEs) and assess their genetic diversity. MDR isolates (with phenotypic resistance to aminoglycosides, macrolides, fluoroquinolones and/or tetracyclines) were primarily found among BRD-affected compared to healthy animals. Non-susceptible isolates, belonging to ST79 and ST13, harbored point mutations and four to nine ARGs, including rarely reported mechanisms in Europe (mph(E), msr(E) and aadA31 ARGs and newly described mutations in the gyrA/parC genes). All ARGs were linked to the presence of MGEs including two ICEs, Tn7407 and the novel Tn7809, a prophage and a putative composite transposon. Clonally related isolates were found in different batches from the same feedlot, suggesting maintenance of MDR strains. Our findings demonstrate the diverse genetic basis of AMR in P. multocida from BRD-affected cattle in Spain, emphasizing the role of MGEs in the ARG dissemination.

Genetic diversity of Salmonella enterica during acute human infections

The ubiquitous bacterial pathogen Salmonella enterica is the causative agent of both enteric fever and gastroenteritis. Despite its significant global health burden, we lack an understanding of its genetic diversity during acute infection, with ramifications for treatment and prevention. Here, we investigated within-host infection diversity of acute salmonellosis using whole-genome sequencing of blood or stool isolates obtained from 23 different patients. We found that intestinal infections exhibited greater genetic variation than blood infections, including in their plasmid content. While same-patient isolates were separated by 10 single nucleotide polymorphisms or less, they often differed in the carriage of genes or alleles, including those associated with antibiotic resistance or virulence. Given the longstanding emphasis on single colony isolation in clinical and laboratory microbiology, these findings have implications for how we both study evolution and transmission and how we treat salmonellosis in an age of increasing antibiotic resistance.

Co-carriage of diverse vancomycin-resistant Enterococcus faecium ST80-lineages by 70% of patients in an Irish hospital

Background

Vancomycin-resistant Enterococcus faecium (VREfm) are significant nosocomial pathogens. Irish VREfm comprise diverse vanA-encoding ST80-complex type (CT) lineages. Recent studies indicate that within-patient VREfm diversity could confound surveillance. This study investigated the intra-host VREfm genetic diversity among colonized Irish hospital patients.

Methods

Rectal VREfm (n = 150) from 10 patients (15 isolates each) were investigated by WGS, core-genome MLST and split k-mer (SKA)-SNP analysis. Plasmids and vanA-transposons from 39 VREfm representative of CTs identified were resolved by hybrid assembly of short-read (Illumina) and long-read (Oxford Nanopore Technologies) sequences. Plasmid relatedness was assessed based on Mash distances. Thirty vancomycin-susceptible E. faecium (VSEfm) from four VREfm-positive patients were also investigated.

Results

All isolates were clade A1 and most were ST80 (VREfm, 147/150; VSEfm, 25/30). Seventy-percent of patients (7/10) harboured either two (n = 4), three (n = 2) or four (n = 1) VREfm CTs. Individual patient isolate pairs from different CTs differed significantly (median SKA-SNPs 2933), but differences were minimal between isolate pairs of the same CT (median SKA-SNPs 0). In total, 193 plasmids were identified in 39 VREfm investigated. Near-identical plasmids (≥99.5% average nucleotide identity) were identified in divergent CTs from multiple patients. Most VREfm (28/39, 72%) harboured vanA on closely related transferable, linear plasmids. Divergent CTs within individual patients harboured either indistinguishable vanA-transposons or vanA-transposons with distinct organizational iterations. Four VSEfm from different CTs investigated harboured similar plasmids to VREfm.

Conclusion

VREfm within-host diversity is highly prevalent in Irish hospital patients, which complicates surveillance. Linear plasmids play an important role in the emergence of Irish VREfm.

Characterization of transferable antibiotic resistance plasmids in airborne particulate matter from ICU environments

Intensive care units (ICUs) are critical environments for the emergence of antibiotic-resistant bacteria, with numerous studies focusing on resistant pathogens in these settings. However, transferable antibiotic resistance plasmids (TARPs)-regardless of their origin from pathogenic or non-pathogenic bacteria-are key drivers of resistance gene dissemination and the emergence of resistant strains. This study investigated TARPs in ICU air. Air samples were directly used to isolate resistant plasmids using Escherichia coli CV601 as the recipient. Plasmid types, antibiotic resistance genes (ARGs), and virulence factors were identified through sequencing, and resistance phenotypes were validated. A total of 30 distinct plasmid types were detected, with IncX3 being the most prevalent. Among 245 ARGs identified, bla NDM-53, bla SHV-12, and BRP(MBL) were dominant. Phylogenetic analysis indicated that these TARPs originated from bacteria commonly colonizing human mucosa. ICU airborne TARPs may significantly contribute to the spread of ARGs and antibiotic resistance transmission.

The dark matter of bacterial genomic surveillance-antimicrobial resistance plasmid transmissions in the hospital setting

Dissemination of antimicrobial resistance (AMR) is a growing global public health burden. The aim of this study was to characterize AMR plasmid transmissions within a tertiary care hospital and identify relevant AMR plasmid transmission pathways. During an 18-month observation period, 540 clinical gram-negative multidrug-resistant bacterial (MDRB) isolates were collected during routine hospital surveillance and subjected to Pacific Biosciences long-read whole genome sequencing. Potential clonal transmissions were determined based on core genome multilocus sequence typing (cgMLST), and plasmid transmissions were detected using a novel real-time applicable tool for plasmid transmission detection. Potential transmissions were validated using epidemiological data. Among the 471 eligible MDRB isolates, we detected 1,539 plasmids; 84.41% of these were circularized. We identified 38 potential clonal transmissions in 24 clusters based on cgMLST and 121 potential plasmid transmissions in 24 clusters containing genetically related AMR plasmids. Among the latter clusters, 10 contained different multilocus sequence types (involving 2-38 isolates, median: 3 isolates), and nine contained multiple species (2-18 isolates, median: 4). Epidemiological data confirmed 19 clonal transmissions (in seven clusters) and an additional 12 plasmid transmissions (within eight plasmid clusters). Among these, we identified seven cases of intra-host and five patient-to-patient plasmid transmissions. We demonstrate that intra-host and patient-to-patient transmissions of AMR plasmids can be identified by combining long-read sequencing with real-time applicable tools during routine molecular surveillance. In addition, our study highlights that more than a decade of bacterial genomic surveillance missed at least one-third of all AMR transmission events due to plasmids.

IMPORTANCE

Antimicrobial resistance (AMR) poses a significant threat to human health. Most AMR determinants are encoded extra-chromosomally on plasmids. Although current infection control strategies primarily focus on clonal transmission of multidrug-resistant bacteria, until today, AMR plasmid transmission routes are neither understood nor analyzed in the hospital setting. In our study, we simultaneously determined both clonal, that is, based on chromosomes, and AMR plasmid transmissions during routine molecular surveillance by combining long-read sequencing with a novel real-time applicable software tool and validated all potential transmission events with epidemiological data. Our analysis determined not only the yet unknown plasmid transmissions within healthcare facilities or within the community but also resulted, in addition to the clonal transmissions, in at least a third more transmissions due to AMR plasmids.

Longitudinal and cross-sectional sampling and whole genome sequencing of Campylobacter in a chicken abattoir reveal highly dynamic population structure

Campylobacter is a leading cause of human gastroenteritis worldwide and is commonly identified in poultry products. Current knowledge of its dissemination patterns in poultry production largely relies on the less sensitive traditional genotyping methods. In this study, whole-genome sequencing was applied to 324 Campylobacter isolates sampled from a chicken abattoir in the Greater Vancouver area throughout 2020. Core genome multi-locus sequence typing analysis revealed a highly diverse and dynamic Campylobacter population containing 27 distinct lineages. A wide range of plasmids was characterized, and a high prevalence of antibiotic resistance was observed among these isolates. Distinct subpopulations were identified in 10 lineages, suggesting that some Campylobacter populations may have diversified within the local agricultural environment. Some lineages were frequently reintroduced to the abattoir, suggesting the potential presence of hidden Campylobacter reservoirs upstream of slaughter. Comparisons between biological and environmental samples suggest a high probability of between-batch cross-contamination. Locally sourced public Campylobacter isolates showed strong genomic correlations with the lineages identified in this study. Notably, lineages 1629a and 1629b were identified to have persisted within the local poultry production ecosystem for several years, explaining their recurrent detection. In conclusion, this study enhances our understanding of Campylobacter population dynamics in the chicken abattoir environment, providing insights for controlling this foodborne pathogen in poultry production systems.IMPORTANCEUsing whole-genome sequencing, this study revealed a highly diverse and dynamic Campylobacter population within the chicken abattoir. The high prevalence of antibiotic resistance marked the critical need for surveillance in this region. The findings highlighted the likely existence of a hidden common source of Campylobacter upstream in the poultry production chain, which significantly contributes to the repeated introduction of the same lineages into the abattoir. Given the frequent reintroductions, the current understanding of Campylobacter persistence in the abattoir environment (up to 21 days) may require revision. Additionally, batch-to-batch dissemination of Campylobacter strains during processing is highly possible. A robust geographic association was also observed between the Campylobacter population in the abattoir and the local community. In sum, this study provides insights into the dynamics of Campylobacter contamination in the poultry production chain, offering guidance for improving prevention and control strategies.

Contaminated drinking water facilitates Escherichia coli strain-sharing within households in urban informal settlements

Identifying bacterial transmission pathways is crucial to inform strategies that limit the spread of pathogenic and antibiotic-resistant bacteria. Here we assessed Escherichia coli strain-sharing and overlap of antibiotic resistance genes (ARGs) across humans, poultry, canines, soil, and drinking water within and between households in urban informal settlements in Nairobi, Kenya. We collected 321 samples from 50 households with half having access to chlorinated water. We performed Pooling Isolated Colonies-seq, which sequences pools of up to five E. coli colonies per sample to capture strain diversity. Pooling Isolated Colonies-seq captured 1,516 colonies and identified 154 strain-sharing events, overcoming limitations of single-isolate sequencing and metagenomics. Within households, strain-sharing rates and resistome similarities across sample types were strongly correlated, suggesting clonal transmission of ARGs. E. coli isolated from the environment carried clinically relevant ARGs. Strain-sharing was rare between animals and humans but frequent between humans and drinking water. E. coli-contaminated stored drinking water was associated with higher human-human strain-sharing within households. These results suggest that contaminated drinking water facilitates human to human strain-sharing, and water treatment can disrupt transmission.

Characterization of a multidrug-resistant hypovirulent ST1859-KL35 klebsiella quasipneumoniae subsp. similipneumoniae strain co-harboring tmexCD2-toprJ2 and blaKPC-2

OBJECTIVES

The rise of multidrug-resistant (MDR) Klebsiella pneumoniae is a significant public health threat. Klebsiella quasipneumoniae is often misidentified as K. pneumoniae, and its genetic and virulence traits remain underexplored. This study characterizes the genomic and phenotypic features of a K. quasipneumoniae subsp. similipneumoniae strain (KP24).

METHODS

Antibiotic susceptibility was tested using microbroth dilution assay. Virulence was evaluated through serum killing assay and Galleria mellonella infection model. Whole genome sequencing (WGS) and bioinformatics analysis determined sequence typing, resistance profiles, and plasmid types. Conjugation assays assessed plasmid transferability, while phylogenetic analysis explored genetic relationships.

RESULTS

KP24 exhibited an MDR phenotype, including resistance to carbapenems, ceftazidime/avibactam, and tigecycline. KP24 showed significantly higher serum survival and G. mellonella lethality than ATCC700603, though it was less virulent than the hypervirulent strain NUTH-K2044. WGS identified KP24 as ST1859 and KL35, harboring the aerobactin virulence gene cluster (iucABCDiutA) and multiple resistance genes, including tmexCD2-toprJ2, blaKPC-2, blaOXA-10, blaIMP-4, and qnrS1. Notably, the tmexCD2-toprJ2 and blaKPC-2 genes were located on the same plasmid (pKP24-1), an uncommon co-existence. Conjugation assays confirmed the independent transferability of pKP24-1 to Escherichia coli J53. Phylogenetic analysis revealed that ST1859 forms a distinct monoclade with low genetic diversity, closely related to ST334, suggesting regional expansion and potential global dissemination.

CONCLUSIONS

KP24 represents a hypovirulent yet multidrug-resistant strain of K. quasipneumoniae subsp. similipneumoniae, with a concerning combination of virulence and resistance determinants. The co-location of tmexCD2-toprJ2 and blaKPC-2 on a transferable plasmid highlights the potential for horizontal gene transfer of critical resistance mechanisms.

Listeria tempestatis sp. nov. and Listeria rocourtiae subsp. hofi subsp. nov

In September 2018, Hurricane Florence resulted in major flooding in North Carolina, USA. Efforts to isolate Listeria monocytogenes and other Listeria spp. from Hurricane Florence floodwaters repeatedly yielded non-haemolytic Listeria-like isolates that could not be readily assigned to known Listeria taxa. Whole-genome sequence analyses against the 28 currently known Listeria species confirmed that the isolates constitute two new taxa within the genus Listeria. Taxon I, with one isolate, showed the highest similarity to Listeria goaensis, with an average nucleotide identity blast of 85.3±4.4% and an in silico DNA-DNA hybridization (isDDH) of 32.4% (range: 30-35%), differing from the latter by its ability to reduce nitrate, ferment d-ribose and sucrose, and by its inability to produce catalase or ferment d-trehalose and d-lactose. Taxon II, represented by 11 isolates, showed the highest similarity to Listeria rocourtiae, with an average nucleotide identity blast of 92.64±3.8% and an isDDH of 49.9% (range: 47.3-52.5%), differing from the latter by its ability to ferment l-arabinose and its inability to ferment l-rhamnose, d-galactose, d-lactose and d-melibiose. The names Listeria tempestatis sp. nov. and Listeria rocourtiae subsp. hofi subsp. nov. are proposed for taxon I and II, respectively, with type strains CLIP 2022/01175T (F6L-1A=CIP 112444T = DSM 117029T) and CLIP 2022/01000T (F66L-1A=CIP 112443T = DSM 117030T), respectively. Both taxa lack known Listeria pathogenic islands, suggesting a lack of pathogenicity for humans.

Emergence of an XDR Klebsiella pneumoniae ST5491 strain co-harboring NDM-5, MCR-1.1, tmexCD1-toprJ1, and a novel plasmid carrying CTX-M-15

Objective

The rapid emergence of antimicrobial resistance (AMR) in Klebsiella pneumoniae poses a significant global health threat. The study aimed to analyze and describe the genomic architecture and resistance mechanisms of an extensively drug-resistant (XDR) K. pneumoniae isolate, KP09, by focusing on plasmids that harbor multiple resistance genes, including tmexCD1-toprJ1, blaCTX-M-15 , blaNDM-5 , and mcr-1.1.

Methods

The KP09 strain, isolated from a clinical sample, was subjected to antimicrobial susceptibility testing and conjugation experiments. Whole-genome sequencing with both long- and short-read methods facilitated hybrid assembly for complete genome reconstruction. Bioinformatics analyses identified resistance genes, plasmid structures, and sequence types (STs), whereas comparative genomic analysis elucidated the context and dissemination mechanisms of resistance determinants.

Results

KP09 exhibited broad-spectrum resistance to carbapenems, colistin, eravacycline, and tigecycline, and only remained susceptible to cefiderocol. The conjugation experiments successfully produced four transconjugants, each carrying specific plasmids: JKP09-1 harbored the tmexCD1-toprJ1 gene, JKP09-2 harbored tmexCD1-toprJ1 and mcr-1.1 genes, JKP09-3 harbored the mcr-1.1 gene, and JKP09-4 harbored blaNDM-5 and mcr-1.1 genes. Genomic analysis revealed a novel IncFIA/IncFII/IncQ1 hybrid plasmid carrying bla CTX-M-15, along with a large conjugative plasmid encoding the tmexCD1-toprJ1 efflux pump. The bla NDM-5 and mcr-1.1 genes were located in separate IncX-type plasmids, suggesting independent dissemination pathways. Furthermore, KP09 was identified as a new sequence type, ST5491, closely related to the endemic ST15 clone. The comparative analysis highlighted the role of mobile genetic elements, such as IS26 and ISEcp1, in facilitating the spread of resistance genes.

Conclusion

This study provides critical information on the genetic mechanisms that drive AMR in K. pneumoniae, including the identification of a novel bla CTX-M-15 encoding IncFIA/IncFII/IncQ1 hybrid plasmid and the emergence of the ST5491 strain. Understanding the genetic basis of resistance is essential to inform public health interventions and mitigate the impact of AMR.

The complete genome sequence of the crayfish pathogen Candidatus Paracoxiella cheracis n.g. n.sp. provides insight into pathogenesis and the phylogeny of the Coxiellaceae family

The Coxiellaceae bacterial family, within the order Legionellales, is defined by a collection of poorly characterized obligate intracellular bacteria. The zoonotic pathogen and causative agent of human Q fever, Coxiella burnetii, represents the best-characterized member of this family. Coxiellaceae establish replicative niches within diverse host cells and rely on their host for survival, making them challenging to isolate and cultivate within a laboratory setting. Here, we describe a new genus within the Coxiellaceae family that has been previously shown to infect economically significant freshwater crayfish. Using culture-independent long-read metagenomics, we reconstructed the complete genome of this novel organism and demonstrate that the species previously referred to as Candidatus Coxiella cheraxi represents a novel genus within this family, herein denoted Candidatus Paracoxiella cheracis. Interestingly, we demonstrate that Candidatus P. cheracis encodes a complete, putatively functional Dot/Icm type 4 secretion system that likely mediates the intracellular success of this pathogen. In silico analysis defined a unique repertoire of Dot/Icm effector proteins and highlighted homologs of several important C. burnetii effectors, including a homolog of CpeB that was demonstrated to be a Dot/Icm substrate in C. burnetii.IMPORTANCEUsing long-read sequencing technology, we have uncovered the full genome sequence of Candidatus Paracoxiella cheracis, a pathogen of economic importance in aquaculture. Analysis of this sequence has revealed new insights into this novel member of the Coxiellaceae family, demonstrating that it represents a new genus within this poorly characterized family of intracellular organisms. Importantly, the genome sequence reveals invaluable information that will support diagnostics and potentially both preventative and treatment strategies within crayfish breeding facilities. Candidatus P. cheracis also represents a new member of Dot/Icm pathogens that rely on this system to establish an intracellular niche. Candidatus P. cheracis possesses a unique cohort of putative Dot/Icm substrates that constitute a collection of new eukaryotic cell biology-manipulating effector proteins.

Extended spectrum beta-lactamase producing Escherichia coli and antimicrobial resistance gene sharing at the interface of human, poultry and environment: results of ESBL tricycle surveillance in Kathmandu, Nepal

BACKGROUND

The spread of antimicrobial resistant pathogens, including extended-spectrum β-lactamase (ESBL) producing Enterobacteriaceae is a global health threat and can be addressed only through a One Health approach. We aimed to characterize ESBL producing Escherichia coli isolates from World Health Organization Tricycle surveillance using data from whole genome sequencing (WGS) to decipher the potential dynamics of their circulation at the human, poultry and environment interface.

METHODS

WGS was performed on 100 non-duplicate representative ESBL E. coli isolates including 28 isolates from humans, 36 from poultry caeca, and 36 from water samples. Minimum Inhibitory Concentration (MIC) was determined using Vitek 2 Compact. WGS was performed on Illumina NextSeq 2000 platform and open-source bioinformatics pipelines were used to analyze WGS data for genomic characterization including phylogenetic analysis and in silico multi-locus sequence typing and, serotyping and, ESBL gene detection.

RESULTS

Most isolates were susceptible to imipenem (98%), meropenem (94%) and tigecycline (94%). Six ESBL E. coli isolates from poultry were resistant to colistin (MIC ≥ 4 μg/ml). WGS revealed high genetic diversity representing 56 sequence types (ST) including three novel STs. ST131 (7 isolates) was the most prevalent comprising human and environment isolates, followed by ST2179 (6 isolates, all poultry) and ST155 (5 isolates across the three sectors). All eight recognized E. coli phylogroups were observed, with majority (86%) of the isolates belonging to A, B1, B2 and D phylogroups. Of the100 isolates, 98 carried blaCTX-M gene, with blaCTX-M-15 the most prevalent allele (76%). AmpC type ESBL genes were found in four and OXA type β lactamases in six isolates. In our study, blaNDM-5 was detected in two imipenem resistant isolates from human. Coexistence of more than one β-lactamase genes was seen in 26% isolates.

CONCLUSION

Our findings indicate high genetic diversity among ESBL E. coli strains from all three sectors and sharing of identical strains and resistance genes within and between sectors. ST131, the globally dominant ESBL E. coli clade is gaining prevalence in Nepal with blaCTX-M being the most common ESBL gene across the phylogroups and all source groups. Antimicrobial stewardship should be promoted in one health approach to combat antimicrobial resistance.

Genomic analysis of carbapenemase-encoding plasmids and antibiotic resistance in carbapenem-resistant Klebsiella pneumoniae isolates from Vietnam, 2021

Carbapenem resistance in gram-negative rods is increasing in low- and middle-income countries. We conducted a single-center study to identify carbapenemase-encoding plasmids in carbapenem-resistant Klebsiella pneumoniae isolates causing human infections in Vietnam. The secondary objective was to investigate the prevalence of multidrug-resistant (MDR) and hypervirulent K. pneumoniae in this setting. Our genomic analysis study characterized 105 of 245 clinical K. pneumoniae isolates at the 108 Military Hospital in Hanoi, Vietnam, collected from intensive care unit and regular wards between 1 January 2021 and 31 December 2021. All isolates were characterized using long- and short-read sequencing, followed by hybrid assembly. Comprehensive genomic analysis was performed to identify carbapenemase-encoding plasmids, complemented by extended antibiotic susceptibility testing for commonly used and novel antibiotics. We observed a high prevalence of NDM-4-related carbapenem resistance (30.5%, 32/105) mostly carried by a specific 83-kb IncFII plasmid co-carrying the blaTEM-1 (46.9%, 15/32). The genomic content of the blaNDM-4-harboring plasmids is highly variable. While blaOXA-181 and blaOXA-48 were predominantly located on an IncX3 and an IncL plasmid, respectively, the majority of plasmids harboring blaKPC-2 were not related to any named Inc-type. All isolates exhibited the MDR phenotype; however, the majority remained susceptible to the siderophore-cephalosporin cefiderocol (79%, 83/105). All isolates were susceptible to aztreonam/avibactam. In addition, we identified a hypervirulent, carbapenem-resistant K. pneumoniae ST23 strain, confirmed through both in vitro and in vivo experiments. Our study provides insights into plasmids harboring the carbapenemases New Delhi metallo-β-lactamase, oxacillinase-48 like, and K. pneumoniae carbapenemase-2 circulating in Vietnam.IMPORTANCECarbapenem resistance in Klebsiella pneumoniae is a major public health threat, especially in low- and middle-income countries. This study examined resistant strains from a hospital in Vietnam to understand how they spread and which antibiotics might still work. We found that a significant number of these bacteria carried resistance genes on different types of plasmids. Despite their resistance to many antibiotics, most strains remained susceptible to newer substances like cefiderocol and aztreonam/avibactam. Alarmingly, we also identified a hypervirulent strain that is carbapenem resistant, potentially posing an even greater risk to patients. This research provides insight into the epidemiology of the carbapenemase gene-harboring plasmids in a Vietnamese hospital. Understanding these resistance patterns can help guide antibiotic use and policy decisions to combat the growing threat of multidrug-resistant infections in Vietnam.

Identification of Novel Staphylococcus aureus Core and Accessory Virulence Patterns in Chronic Rhinosinusitis

Staphylococcus aureus (S. aureus) colonizes the nasal cavities of both healthy individuals and patients with chronic rhinosinusitis (CRS) with (CRSwNP) and without (CRSsNP) nasal polyps. Treatment-resistant S. aureus biofilms and intracellular persistence are common in CRS patients, requiring the expression of specific virulence factor genes to transition into these forms. We hypothesized that S. aureus isolates from non-diseased controls, CRSsNP patients, and CRSwNP patients would exhibit distinct virulence factor patterns contributing to persistence and intracellular survival in CRS patients. Nasal swabs from seventy-seven individuals yielded S. aureus cultures in eight non-diseased controls, eight CRSsNP patients, and five CRSwNP patients. Whole-genome sequencing analyzed stress, antimicrobial resistance, and virulence genes, including plasmids and prophages. Four virulence factor gene patterns emerged: a core set (hlgA, icaC, hlgB, hlgC, hld, and aur) present in all isolates, and accessory sets, including the enterotoxin gene cluster (seo, sem, seu, sei, and sen) and a partial/complete invasive virulence factor set (splE, splA, splB, lukE, and lukD) (p = 0.001). CRSwNP isolates exhibited incomplete carriage of the core set, with frequent loss of scn, icaC, and hlgA (p < 0.05). These findings suggest that S. aureus has clusters of virulence factors that may act in concert to support the survival and persistence of the bacteria, resulting in enhanced pathogenicity. This may manifest clinically with resistant disease and refractoriness to antibiotics.

Complete genome sequence of Escherichia marmotae F12YCO47 isolated from a healthy human fecal sample

Escherichia marmotae has been found in animals and the environment. Here, we isolated it from a healthy human fecal sample. The 4.91 Mb circular genome (GC content = 50.34%) is associated with three plasmids: pF12YCO47-2 (89.9 kb, 50.2% GC), pF12YCO47-3 (47.9 kb, 44.3% GC), and pF12YCO47-1 (95.4 kb, 47.2% GC).

In silico genomic insights into bacteriophages infecting ESBL-producing Escherichia coli from human, animal, and environmental sources

BACKGROUND

The emergence of antimicrobial resistance (AMR) in Escherichia coli, particularly extended-spectrum beta-lactamase-producing E. coli (ESBL-EC), is a global public health concern. Bacteriophages (phages) play a significant role in bacterial evolution and the spread of antibiotic resistance genes (ARGs). This study investigates prophages integrated within ESBL-EC genomes to assess their diversity, gene content, and potential contributions to ESBL-EC persistence across human, animal, and environmental reservoirs. Between May and December 2020, a cross-sectional study was conducted in Abuja and Lagos, collecting 448 stool, cecal, and environmental samples from abattoir workers, slaughtered cattle, and the abattoir environment. ESBL-EC genomes from these samples, obtained in an earlier study, were analyzed for phage regions using PHASTER. Intact prophages were analyzed in silico using computational tools to detect ARGs, ESBL genes, virulence factors, and heavy metal resistance. Their genomic relationships were examined with statistical significance of p < 0.05.

RESULTS

Out of 448 samples, ESBL-EC prevalence was 21.7% (97/448). Among 97 ESBL-EC isolates, 646 prophage regions were detected, with 30% (194/646) classified as intact phages. Among the 158 phages with genus assignments, Punavirus was the most prevalent (60.1%). Escherichia was the most frequent predicted host (308/646), particularly in cattle (n = 143) and human (n = 124) sources. Among ESBL-EC genomes, 83.5% (81/97) with intact phages carried phage-associated ARGs, 76.3% (74/97) carried phage-associated ESBL genes, 18.6% (18/97) harbored phage-associated virulence factors, 15.5% (15/97) contained phage-associated plasmids, and 10.3% (10/97) had heavy metal resistance. The most prevalent phage-associated ARGs detected were qnrS1 (73/81) and blaCTX-M-15 (72/81). Two isolates recovered from abattoir workers carried two phage-like plasmids, each harboring either tet(A) or blaCTX-M-55 gene. The predominant phage lifestyles were temperate (n = 182), mainly in the Peduoviridae family, and lytic (n = 12) in the Punavirus genus.

CONCLUSION

This is the first study in Nigeria to characterize phages in ESBL-EC isolates at the One Health interface. The presence of intact phages in humans, animals, and the environment underscores the complex interactions shaping phage ecology. The discovery of ARGs, virulence genes, and heavy metal resistance within prophages suggests a potential role in AMR dissemination. Future research should focus on elucidating mechanisms of ARG transfer mediated by phages in One Health settings.

Molecular epidemiology of Salmonella Enteritidis in humans and animals in Spain

Salmonella Enteritidis, the most prevalent serovar-causing human gastroenteritis, has been traditionally linked to poultry sources. Although antimicrobial resistance (AMR) is not common in this serovar, increasing levels of resistance to fluoroquinolones and ampicillin have been reported in the last few years. Here, 298 isolates retrieved from different sources (human, livestock, wildlife, food, and environment) and years (2002-2021) in Spain were analyzed to evaluate their diversity, the distribution of AMR-conferring genes (ARGs), and mutations and reconstruct the epidemiology of infection due to this serovar. Isolates were clustered in two major clades (I and II), with strains in clade I (including 61.5% of all human isolates) displaying a pan-susceptible phenotype and not carrying AMR determinants. In contrast, clade II included 80.7% of isolates from animal/food/environmental sources, with the majority (69.8%) harboring mutations in the quinolone resistance determinant regions (QRDR). ARGs, although rare, were mostly found in clade II strains that also carried plasmid replicons, among which IncX1 was the most common. Although higher levels of phenotypic resistance were found in animal isolates, extended-spectrum beta-lactamase, plasmid-mediated AmpC, and carbapenemase-encoding genes were only found among human isolates. In summary, the majority of human and animal isolates from Spanish sources in our collection were classified in different phylogenetic branches, suggesting that additional sources are contributing to the occurrence of foodborne infections in Spain. Furthermore, the different distributions of virulence factors and ARGs in isolates from different sources and their association with specific plasmids suggest the presence of different dynamics contributing to the selection of resistant strains.

Evolution of ceftazidime/avibactam resistance and plasmid dynamics in OXA-48-producing Klebsiella spp. during long-term patient colonization

PURPOSE

To prospectively monitor the evolution of the resistome of OXA-48-producing Klebsiella species in a patient with long-term colonization, with a particular focus into the plasmid dynamics and the evolution of ceftazidime/avibactam resistance.

METHODS

All OXA-48-producing Klebsiella spp. isolates from a single patient admitted to a hospital during seven months were prospectively collected. MICs were determined through reference broth microdilution. Multilocus sequence types, SNPs analysis, resistance mechanisms, genetic context of β-lactamases and plasmid dynamics were determined by WGS and bioinformatic analysis. The impact of β-lactamase variant obtained after ceftazidime/avibactam exposure was determined via cloning experiments.

RESULTS

Four isolates, two before (one OXA-48-producing K. pneumoniae and one CTX-M-15-like-producing K. pneumoniae) and two after treatment with ceftazidime/avibactam (one OXA-48- and CTX-M-15-like-producing K. pneumoniae and one OXA-48- and CTX-M-15-like-producing K. aerogenes) were collected. The plasmid dynamics analysis demonstrated that the IncL and IncFIIK plasmids, in which blaOXA-48 and blaCTX-M-15-like genes were located, respectively, exhibited a high degree of conservation indicating a potential for both intra- and interspecies transmission. The K. pneumoniae isolate obtained after treatment, which differed from the previous isolate by just six SNPs, exhibited resistance to ceftazidime/avibactam through P167S substitution in CTX-M-15, which is now designated CTX-M-273. Cloning experiments demonstrated enhanced resistance to ceftazidime/avibactam.

CONCLUSION

The transfer of plasmid-borne β-lactamase resistance genes between intra- and interspecies bacterial populations enables the rapid diversification of the bacterial genome. The emergence of ceftazidime/avibactam resistance through the modification of CTX-M-enzymes represents a mechanism by which OXA-48-producing Enterobacterales may evolve toward ceftazidime/avibactam resistance in vivo.

Probiogenomics of Leuconostoc Mesenteroides Strains F-21 and F-22 Isolated from Human Breast Milk Reveal Beneficial Properties

Bacteria of the Leuconostoc genus are Gram-positive bacteria that are commonly found in raw milk and persist in fermented dairy products and plant food. Studies have already explored the probiotic potential of L. mesenteroides, but not from a probiogenomic perspective, which aims to explore the molecular features responsible for their phenotypes. In the present work, probiogenomic approaches were applied in strains F-21 and F-22 of L. mesenteroides isolated from human milk to assess their biosafety at the molecular level and to correlate molecular features with their potential probiotic characteristics. The complete genome of strain F-22 is 1.99 Mb and presents one plasmid, while the draft genome of strain F-21 is 1.89 Mb and presents four plasmids. A high percentage of average nucleotide identity among other genomes of L. mesenteroides (≥ 96%) corroborated the previous taxonomic classification of these isolates. Genomic regions that influence the probiotic properties were identified and annotated. Both strains exhibited wide genome plasticity, cell adhesion ability, proteolytic activity, proinflammatory and immunomodulation capacity through interaction with TLR-NF-κB and TLR-MAPK pathway components, and no antimicrobial resistance, denoting their potential to be candidate probiotics. Further, the strains showed bacteriocin production potential and the presence of acid, thermal, osmotic, and bile salt resistance genes, indicating their ability to survive under gastrointestinal stress. Taken together, our results suggest that L. mesenteroides F-21 and F-22 are promising candidates for probiotics in the food and pharmaceutical industries.

In-depth characterization of Klebsiella pneumoniae carbapenemase (KPC)-encoding plasmids points at transposon-related transmission of resistance genes

Antimicrobial resistance (AMR) is a growing threat in healthcare systems, particularly in the management of infections in critically ill patients. This study highlights how to identify clusters and putative sharing of mobile genetic elements, such as transposons, in the hospital setting using long-read whole genome sequencing (lrWGS). The approach described here can be employed to investigate the transmission dynamics of KPC-3-positive Klebsiella pneumoniae at multiple levels, from the entire isolate down to individual plasmids and transposons. Here, a bla KPC-3 harboring transposon cluster was identified by using a Mash-based distance calculation for plasmids. This approach was used to investigate a local accumulation of KPC-3-positive Klebsiella pneumoniae on surgical and infectious disease wards of a tertiary care center in Germany over a time of six months. In total, seven patients were affected. Core genome multi-locus sequence typing analysis (cgMLST) identified two distinct genetic clusters: a sequence type (ST) 307 cluster (n = 5) and a ST101 cluster (n = 2). All isolates carried a bla KPC-3 carbapenemase. Further Mash distance-based plasmid analysis was not consistent with plasmid transfer due to genetic heterogeneity, but identified a transposon cluster across all isolates. Infection control evaluation of patient movements within their hospital admission supports a possible clonal transmission. Subsequent infection control measures, including point prevalence screening and enhanced contact precautions, successfully contained further transmissions. The study illustrates the value of in-depth plasmid analysis in understanding the transmission dynamics and epidemiology of AMR, particularly in hospital environments.

Machine learning reveals the dynamic importance of accessory sequences for Salmonella outbreak clustering

Bacterial typing at whole-genome scales is now feasible owing to decreasing costs in high-throughput sequencing and the recent advances in computation. The unprecedented resolution of whole-genome typing is achieved by genotyping the variable segments of bacterial genomes that can fluctuate significantly in gene content. However, due to the transient and hypervariable nature of many accessory elements, the value of the added resolution in outbreak investigations remains disputed. To assess the analytical value of bacterial accessory genomes in clustering epidemiologically related cases, we trained classifiers on a set of genomes collected from 24 Salmonella enterica outbreaks of food, animal, or environmental origin. The models demonstrated high precision and recall on unseen test data with near-perfect accuracy in classifying clonal and short-term outbreaks. Annotating the genomic features important for cluster classification revealed functional enrichment of molecular fingerprints in genes involved in membrane transportation, trafficking, and carbohydrate metabolism. Importantly, we discovered polymorphisms in mobile genetic elements (MGEs) and gain/loss of MGEs to be informative in defining outbreak clusters. To quantify the ability of MGE variations to cluster outbreak clones, we devised a reference-free tree-building algorithm inspired by colored de Bruijn graphs, which enabled topological comparisons between MGE and standard typing methods. Systematic evaluation of clustering MGEs on an unseen dataset of 34 Salmonella outbreaks yielded mixed results that exemplified the power of accessory sequence variations when core genomes of unrelated cases are insufficiently discriminatory, as well as the distortion of outbreak signals by microevolution events or the incomplete assembly of MGEs.

IMPORTANCE

Gene-by-gene typing is widely used to detect clusters of foodborne illnesses that share a common origin. It remains actively debated whether the inclusion of accessory sequences in bacterial typing schema is informative or deleterious for cluster definitions in outbreak investigations due to the potential confounding effects of horizontal gene transfer. By training machine learning models on a curated set of historical Salmonella outbreaks, we revealed an enriched presence of outbreak distinguishing features in a wide range of mobile genetic elements. Systematic comparison of the efficacy of clustering different accessory elements against standard sequence typing methods led to our cataloging of scenarios where accessory sequence variations were beneficial and uninformative to resolving outbreak clusters. The presented work underscores the complexity of the molecular trends in enteric outbreaks and seeks to inspire novel computational ways to exploit whole-genome sequencing data in enteric disease surveillance and management.

Genomic epidemiology and public health implications of zoonotic monophasic Salmonella Typhimurium ST34

Background

Monophasic Salmonella Typhimurium sequence type 34 (mSTM ST34) has emerged as a significant global health threat, but our understanding of its genomic epidemiology and potential public health implications in international and regional contexts remains limited. This study aims to fill this crucial gap by assessing the genomic epidemiology of multidrug resistance (MDR) mSTM ST34, as well as its clinical characteristics and virulence.

Methods

To achieve the objectives of this study, we conducted a comprehensive genomic analysis of mSTM ST34 isolates. We obtained a global dataset comprising 13,844 strains from public databases, along with 339 strains from a regional surveillance collection in Zhejiang Province, China. This dataset aims to provide in-depth insights into antimicrobial resistance, mobile genetic elements, and pathogenicity. Additionally, we meticulously assessed the association between phenotypic profiles and clinical presentations.

Results

Our findings revealed that the prevalence of mSTM ST34 has surpassed that of the previously dominant ST19. In addition, we observed an increase in the detection of the IncQ1 plasmid, which is responsible for disseminating MDR. The prevalence of mSTM ST34 carriage was exceptionally high among children (≤12 years old) and elderly individuals (≥65 years old), with 92.6% of the isolates exhibiting MDR, including resistance to frontline antimicrobials such as third-generation cephalosporins and ciprofloxacin. Additionally, the human mSTM ST34 strain demonstrates a remarkable capacity for biofilm formation, which increases its virulence in animal models and complicates therapeutic interventions.

Conclusions

mSTM ST34 has surpassed the previously dominant ST19, and its ability to transmit across multi-species increases its potential for further human transmission. This study addresses critical gaps in our understanding of mSTM ST34 prevalence, highlighting the importance of whole genome sequencing in surveilling zoonotic pathogens.

skDER & CiDDER: two scalable approaches for microbial genome dereplication

An abundance of microbial genomes have been sequenced in the past two decades. For fundamental comparative genomic investigations, where the goal is to determine the major gain and loss events shaping the pangenome of a species, it is often unnecessary and computationally onerous to include all available genomes in studies. In addition, over-representation of specific lineages due to sampling and sequencing bias can have undesired effects on evolutionary analyses. To assist users with genomic dereplication, selecting a subset of representative genomes, for downstream comparative genomic investigations, we developed skDER & CiDDER (https://github.com/raufs/skDER). skDER combines recent advances to efficiently estimate average nucleotide identity (ANI) between thousands of microbial genomes with two efficient algorithms for genomic dereplication. Further, CiDDER implements an approach whereby protein clusters are determined across all genomes and genomes are iteratively selected as representatives until a user-defined saturation of the total protein space is achieved. To support ease of use, several auxiliary functionalities are implemented within the two programs, including arguments to: (i) test the number of representative genomes resulting from a variety of clustering parameters, (ii) automate downloading of genomes belonging to a bacterial species or genus by name, (iii) cluster non-representative genomes to their closest representative genomes, and (iv) automatically filter predicted plasmids and phages prior to dereplication. We further assess the effects of filtering mobile genetic elements (MGEs) on ANI and alignment fraction (AF) estimates between pairs of genomes and find that MGEs tend to slightly deflate both metrics in one species.

Double carbapenemases in Klebsiella pneumoniae blood isolates: dissemination in a single medical center via multiple plasmids and a variety of highly efficient clones

Acquisition of multiple carbapenemase genes by Klebsiella pneumoniae (Kp) is an emerging public health threat. Here, we aim to elucidate the population structure of Kp blood isolates carrying two different carbapenemase genes and identify the mechanism facilitating their dissemination. The study was conducted in a tertiary healthcare center between 2014 and 2022. Twenty-four patients with bacteremia caused by Kp carrying two different carbapenemase genes were identified. All 24 blood isolates were analyzed by short-read genome sequences supplemented by long reads in a selected number of isolates. All isolates carried blaKPC (23 blaKPC-2, 1 blaKPC-3) and blaVIM-1 genes, along with a variety of antimicrobial resistance determinants. The isolates were clustered in six clonal lineages (ST39, ST147, ST323, ST258, ST3035, and ST340). Long-read genome sequences demonstrated that each carbapenemase gene was located in a separate group of plasmids: the blaKPC-2 on a fusion of IncFIB(pQil) and IncFII(K) plasmids, the blaKPC-3 on IncX3, the blaVIM-1 on IncC, or a fusion of the IncFIB(pNDM-Mar) and IncHI1B(pNDM-MAR) plasmids. Comparison of plasmid content of eight isolates carrying a single carbapenemase gene from a previous study with eight isolates carrying two carbapenemase genes from the present study, matched by clonal lineages, revealed that the second carbapenemase gene was acquired by addition of another plasmid. Identical plasmids were found within the same lineage and across lineages. These findings suggest that dissemination of carbapenemase genes in our hospital setting was driven by multiple plasmids across a variety of highly efficient clones.

Genomic insights into the plasmidome of non-tuberculous mycobacteria

BACKGROUND

Non-tuberculous mycobacteria (NTM) are a diverse group of environmental bacteria that are increasingly associated with human infections and difficult to treat. Plasmids, which might carry resistance and virulence factors, remain largely unexplored in NTM.

METHODS

We used publicly available complete genome sequence data of 328 NTM isolates belonging to 125 species to study gene content, genomic diversity, and clusters of 196 annotated NTM plasmids. Furthermore, we analyzed 3755 draft genome assemblies from over 200 NTM species and 5415 short-read sequence datasets from six clinically relevant NTM species or complexes including M. abscessus, M. avium complex, M. ulcerans complex and M. kansasii complex, for the presence of these plasmids.

RESULTS

Between one and five plasmids were present in approximately one-third of the complete NTM genomes. The annotated plasmids varied widely in length (most between 10 and 400 kbp) and gene content, with many genes having an unknown function. Predicted gene functions primarily involved plasmid replication, segregation, maintenance, and mobility. Only a few plasmids contained predicted genes that are known to confer resistance to antibiotics commonly used to treat NTM infections. Out of 196 annotated plasmid sequences, 116 could be grouped into 31 clusters of closely related sequences, and about one-third were found across multiple NTM species. Among clinically relevant NTM, the presence of NTM plasmids showed significant variation between species, within (sub)species, and even among strains within (sub)lineages, such as dominant circulating clones of Mycobacterium abscessus.

CONCLUSIONS

Our analysis demonstrates that plasmids are a diverse and heterogeneously distributed feature in NTM bacteria. The frequent occurrence of closely related putative plasmid sequences across different NTM species suggests they may play a significant role in NTM evolution through horizontal gene transfer at least in some groups of NTM. However, further in vitro investigations and access to more complete genomes are necessary to validate our findings, elucidate gene functions, identify novel plasmids, and comprehensively assess the role of plasmids in NTM.

MOSTPLAS: a self-correction multi-label learning model for plasmid host range prediction

MOTIVATION

Plasmids play an essential role in horizontal gene transfer, aiding their host bacteria in acquiring beneficial traits like antibiotic and metal resistance. There exist some plasmids that can transfer, replicate, or persist in multiple organisms. Identifying the relatively complete host range of these plasmids provides insights into how plasmids promote bacterial evolution. To achieve this, we can apply multi-label learning models for plasmid host range prediction. However, there are no databases providing the detailed and complete host labels of these broad-host-range plasmids. Without adequate well-annotated training samples, learning models can fail to extract discriminative feature representations for plasmid host prediction.

RESULTS

To address this problem, we propose a self-correction multi-label learning model called MOSTPLAS. We design a pseudo label learning algorithm and a self-correction asymmetric loss to facilitate the training of multi-label learning model with samples containing some unknown missing labels. We conducted a series of experiments on the NCBI RefSeq plasmid database, the PLSDB 2025 database, plasmids with experimentally determined host labels, the Hi-C dataset, and the DoriC dataset. The benchmark results against other plasmid host range prediction tools demonstrated that MOSTPLAS recognized more host labels while keeping a high precision.

AVAILABILITY AND IMPLEMENTATION

MOSTPLAS is implemented with Python, which can be downloaded at https://github.com/wzou96/MOSTPLAS. All relevant data we used in the experiments can be found at https://zenodo.org/doi/10.5281/zenodo.14708999.

Genomic and phenotypic insight into antimicrobial resistance of Pseudomonas fluorescens from King George Island, Antarctica

The genus Pseudomonas includes metabolically versatile microorganisms occupying diverse niches, from environmental habitats to plant pathogens, and has clinically significant strains. For this reason, Pseudomonas spp. might act as a reservoir of antimicrobial resistance genes, which have been detected even in isolated environments. The aim of this study was to report the antimicrobial susceptibility profile of 25 Pseudomonas fluorescens isolates from soil samples collected on King George Island (Antarctic Peninsula), and to select non-clonal isolates with unusual phenotypes for whole genome sequencing (WGS). Six classes of antimicrobials were assessed with disk diffusion and colistin with minimum inhibitory concentration (MIC) by broth microdilution. In order to confirm the discrepant phenotypes, MIC by agar dilution was performed for the beta-lactams aztreonam, ceftazidime, cefepime and the aminoglycoside neomycin. The genus Pseudomonas was confirmed by matrix-assisted laser desorption/ionization - time of flight (MALDI-TOF) and the clonal relationships were examined using repetitive extragenic palindromic polymerase chain reaction (BOX-PCR), from which 14 strains were selected for WGS. Antimicrobial susceptibility testing revealed that all strains were susceptible to neomycin and exhibited varying degrees of intermediate or full resistance to aztreonam and colistin. Additionally, 11 strains demonstrated intermediate resistance to ceftazidime, and six were resistant to cefepime. The genomic analysis identified various efflux pumps, predominantly from the ABC transporter and resistance-nodulation-division families. Resistance genes were detected against eight classes of antimicrobials, listed by prevalence: beta-lactams, tetracyclines, polymyxins, aminoglycosides, fosmidomycin, fosfomycin, quinolones, and chloramphenicol. Genes associated with heavy-metal resistance, prophages, and adaptations to extreme environments were also investigated. One notable isolate exhibited not only the highest number of pathogenicity and resistance islands, but also presented a carbapenemase-encoding gene (bla PFM-2) in its genome. Overall, one plasmid was identified in a distinct isolate, which did not exhibit antimicrobial resistance determinants. The genotypic and phenotypic findings are consistent, suggesting that efflux pumps play a critical role in antimicrobial extrusion. This study offers valuable insight into the evolution of antimicrobial resistance in P. fluorescens, particularly in extreme environments, such as Antarctica. By exploring the antimicrobial resistance mechanisms in P. fluorescens, the study sheds light on how isolated ecosystems drive the natural evolution of resistance genes.

Characterization of antibiotic determinants and heavy metal resistance genes in Escherichia coli from pigs in Catalonia

More antibiotics are administered to livestock animals than to treat human infections. Industrialization, large animal densities and early weaning mean pigs are exposed to more antibiotics than any other livestock animal. Consequently, antimicrobial resistance (AMR) is common among commensal and pathogenic bacteria. Heavy metals (HMs) are also often used as feed additives for growth promotion and infection prevention alongside antimicrobials, and increased exposure to copper, zinc and cadmium can further encourage AMR through co-selection. In this study, we sequenced an archived collection of 112 Escherichia coli isolates from pigs in Catalonia using short- and long-read sequencing methods to detect AMR and HM tolerance genes. The most common AMR genes were mdfA (84.8%), aph(3″)-Ib (52.7%), bla TEM-1B (45.6%) and aph(6)-Id (45.6%). Genes relevant to public health, such as the extended-spectrum β-lactamases (15.4%), bla CTX-M type or bla SHV, or mobile colistin resistance (mcr) genes (13.4%), such as mcr-1, were also found. HM tolerance genes were present in almost every genome but were rarely located in plasmids, and, in most cases, AMR and HM tolerance genes were not located on the same plasmids. Of the genes predicted to increase tolerance to HMs, only those with activity to mercury were co-located on plasmids alongside other AMR determinants. However, mercury is rarely used in pig farming and does not support a scenario where AMR and HM genes are co-selected. Finally, we identified the exclusive association between mcr-4 and ColE10 plasmid, which may help target interventions to curtail its spread among pig Escherichia coli.

Genomic and phylogenetic analysis of hypervirulent Klebsiella pneumoniae ST23 in Ireland

Hypervirulent Klebsiella pneumoniae (hvKp) has emerged as a pathogen of global concern associated with invasive community-acquired infections. The combination of hypervirulence and carbapenem resistance can result in severe and difficult-to-treat infections. This retrospective study aimed to investigate the spread of hvKp sequence type 23 (ST23) in Ireland and the convergence of hypervirulent (hv) and antimicrobial resistance genotypes. Short-read sequences (PE300) for 90 K. pneumoniae ST23 isolates were generated by the Galway Reference Laboratory Services (GRLS). Isolates were from screening swabs (n=59), invasive infections (n=18), non-invasive sites (n=12) and the hospital environment (n=1). The virulence and resistance content were assessed genomically using Kleborate (v2.2.0), ABRicate (v1.0.1) and Platon (v1.6). The in vivo virulence of the isolates was assessed using a murine model. All isolates were genotypically hv with 88/90 isolates having a maximal Kleborate virulence score of 5 including carriage of key genes. Eighty-two per cent of isolates (74/90) carried a carbapenemase gene (bla OXA-48/bla OXA-181/bla NDM-1), and 42% carried resistance genes to 3 or more antimicrobial classes. Core genomic delineation revealed the isolates to be clonal with similar resistance and virulence profiles. Two distinct clusters of Irish isolates were detected consisting of 82/90 of the isolates. Isolates associated with carriage and infection demonstrated similar in vivo virulence. An established clone of hvKp ST23 is circulating within Ireland and causing both colonization and infection of patients. The lack of reliable screening methods for hvKp makes its detection and control in the healthcare setting challenging.

Mycobacterium servetii sp. nov., a novel rapid-growing nontuberculous mycobacterial species recovered from a human patient in Zaragoza, Spain

In this study, we describe a novel rapid-growing Mycobacterium species isolated from a clinical specimen obtained from the lower respiratory tract of a patient with ciliary dysfunction, bronchiectasis and exacerbated respiratory symptoms. A comprehensive phenotypic characterization was conducted, including the establishment of a MALDI-TOF MS profile. Additionally, whole-genome sequencing was performed to assess overall genomic relatedness indices and conduct phylogenetic comparative analyses. These findings allowed us to characterize a previously unrecognized rapid-growing Mycobacterium species, for which we propose the name Mycobacterium servetii (=DSM 118141; =CECT 31091).

Dentiradicibacter hellwigii gen. nov., sp. nov., isolated from a secondary infected root canal in the human oral cavity

A motile, rod-shaped and anaerobic strain WK13T was isolated from a secondary root canal infection of a human tooth. WK13T cells were Gram-stain-negative, catalase-positive and oxidase-negative. The major fatty acids (≥ 5.0%) were C16 : 0, C18 : 0, C16 : 1  ω7c, C18 : 1  ω9c and C18 : 2  ω6,9c. The DNA G+C content was 57.94 mol%. The major polar lipids were phosphatidylethanolamine, phosphatidylserine, diphosphatidylglycerol, phosphatidylcholine and lysophosphatidylcholine. There were no respiratory quinones detectable. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain WK13T belongs to the class Betaproteobacteria. WK13T showed a 93.6% and 93.5% 16S rRNA gene sequence similarity to the most closely related cultured species, Propionivibrio pelophilus strain DSM 12018T and Propionivibrio dicarboxylicus strain DSM 5885T, respectively. On the basis of physiological and biochemical data, the isolate is considered to represent a novel species of a new genus in the class Betaproteobacteria, for which we propose the name Dentiradicibacter hellwigii gen. nov., sp. nov. The type strain is WK13T (=DSM 112713T=NCTC 14938T).

Increased Severity of Multidrug-Resistant Shigella sonnei Infections in People Experiencing Homelessness

BACKGROUND

Shigella sonnei has caused sexually transmitted enteric infections in men who have sex with men (MSM) in Vancouver. We recently observed a high rate of multidrug-resistant (MDR) S. sonnei bacteremia among persons experiencing homelessness (PEH). We aimed to describe the wider epidemiology, clinical outcomes, and genomics of S. sonnei infections over time.

METHODS

A retrospective review of 163 patients with S. sonnei infections was undertaken from 2015 to 2022. We collected demographic, clinical, and microbiological data over 2 time periods: historical (2015-2020) and recent (2021-2022). Severe shigellosis definition included hospitalization, bacteremia, or death. Whole-genome sequencing was performed to identify genotype, infer relatedness, and predict antimicrobial resistance.

RESULTS

S. sonnei infections increased from 8.3 (historical period) to 56.5 (recent period) cases/year. Over time, the primary population characteristics associated with shigellosis shifted from MSM (45; 98%) to PEH (86; 77%). The population intersection between MSM and PEH historically and recently was similar and occurred in 3 (6%) and 10 (9%) of patients, respectively. Severe shigellosis was significantly higher in the recent versus historical period (69 [61%] vs 7 [14%]; P < .001). A dominant clone of MDR S. sonnei, 3.6.1.1.2 (CipR.MSM5), emerged with resistance to all first- and second-line agents, yet with susceptibility to ceftriaxone.

CONCLUSIONS

We observed a substantial increase in severe shigellosis and shift from sexually transmitted S. sonnei infections in MSM to likely environmental transmission among PEH. More severe disease associated with the 3.6.1.1.2 clone of MDR S. sonnei in PEH could be a result of underlying vulnerabilities of the affected population.

Comprehensive genomic insights into a highly pathogenic clone ST656 of mcr8.1 containing multidrug-resistant Klebsiella pneumoniae from Bangladesh

Antimicrobial resistance (AMR) is a pressing global health issue, intensified by the spread of resistant pathogens like Klebsiella pneumoniae (K. pneumoniae), which frequently causes hospital-acquired infections. This study focuses on a multidrug-resistant K. pneumoniae sequence type (ST) 656 strain, isolated from canal water in Bangladesh. Whole-genome sequencing and comparative genomic analysis revealed extensive resistance mechanisms and genetic elements underlying its adaptability. The strain exhibited resistance to colistin and multiple β-lactam antibiotics, containing key resistance genes such as mcr8.1, blaLAP-2, blaTEM-1, blaSHV-11 and blaOXA-1, alongside genes for copper, zinc, and silver resistance, indicating survival capability in metal-rich environments. Virulence factor analysis identified genes supporting adhesion, biofilm formation, and immune evasion, amplifying its pathogenic potential. Plasmid and phage analyses revealed mobile genetic elements, highlighting the role of horizontal gene transfer in AMR dissemination. The study included a pangenome analysis using a dataset of 32 publicly available K. pneumoniae sequence type (ST) 656 genomes, demonstrating evidence of an expanding pangenome for K. pneumoniae ST656. This study emphasized the role of environmental sources in AMR spread and the importance of continued surveillance, particularly in settings with intensive antibiotic usage, to mitigate the spread of high-risk, multidrug-resistant clones like K. pneumoniae ST656.

Molecular epidemiology and genetic dynamics of carbapenem-resistant hypervirulent Klebsiella pneumoniae in China

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CRhvKP) poses a significant global health threat due to its enhanced virulence and resistance. This study analyzed 5,036 publicly available K. pneumoniae genomes from China (2005-2023), identifying 1,538 CRhvKP genomes, accounting for 44.6% of carbapenem-resistant isolates and 69.5% of hypervirulent isolates. Predominant carbapenemases included bla KPC (92.1%), with an increasing prevalence of bla NDM and bla OXA-48-like genes. Most isolates (93.6%) carried both aerobactin and yersiniabactin genes. The genetic background showed high diversity, characterized by 36 sequence types (STs) and 22 capsule types, with high-risk endemic STs such as ST11, ST15, and ST23 being predominant. ST23 demonstrated enhanced virulence, whereas ST11 carried more resistance genes but showed minimal presence of iroBCDN genes. A core genome MLST analysis revealed that 89.0% of CRhvKP isolates clustered into 131 clonal groups, indicating widespread dissemination, particularly in eastern China. CR and hv plasmids, primarily IncF, IncH, and IncR types, showed distinct community structures, with CR plasmids demonstrating higher mobility and diversity. Crucially, we identified 40 CR-hv convergent plasmids across five STs, likely resulting from plasmid fusions, which have become increasingly prevalent in eastern China over the last decade. Furthermore, chromosomal integration of hv genes and bla KPC-2 was detected, underscoring the stable inheritance of these traits. Class 1 Integrons were present in 84.5% of CRhvKP strains, most notably in ST11 and least in ST23. These integrons harbored genes that confer resistance to various antibiotics, including bla IMP and bla VIM, with their content varying across different STs. This study highlights the genetic complexity, rapid dissemination, and increasing prevalence of CRhvKP in China, emphasizing the urgent need for enhanced genomic surveillance and targeted interventions to mitigate the threat posed by these multidrug-resistant and hypervirulent strains.

Genomic and phenotypic characterization of Chryseomicrobium imtechense from canine pyometra

Chryseomicrobium imtechense is a bacterium primarily isolated in environment samples. Here we demonstrated the virulent and antimicrobial resistant profile of the C. imtechense LBV029/19 strain, which was isolated in a pyometra infection in canines, being related as causal agent of that disease. The bacterium was recovered from purulent content of a uterus with pyometra and the identity was confirmed by both, biochemical tests followed MALDI-TOF MS and 16S-rDNA gene sequencing. Antimicrobial susceptibility test, biofilm formation assessment, genomic sequencing with Illumina MiSeq platform followed by the genome characterization and phylogenetic relationships were conducted with C. imtechense LBV029/19 strain. The phylogenetic analysis revealed a close evolutionary relationship between the C. imtechense LBV029/19 and the others publicly available 16S-rDNA genes of C. imtechense. The in vitro assays shown that C. imtechense LBV029/19 has a strong ability for biofilm formation. Additionally, the antimicrobial susceptibility tests revealed a smaller inhibition zone for novobiocin, cefuroxime, and erythromycin. To the best of our knowledge the C. imtechense LBV029/19 genome is the first genome sequenced and available of C. imtechense. Regarding the genotypic profile, resistance genes to tetracyclines, fluoroquinolones, beta-lactams, and multidrug resistance were present in this genome. Additionally, genes encoded to virulence factors, including biofilm formation, motility, and sporulation were identified. The phenotypic profile associated with the genotypic description indicates the potential of C. imtechense LBV029/19 as a primary agent of animal infectious diseases. The genomic description will contribute to the understanding of the biology of the bacterium and the pathogenesis process involved in the disease.

Kalamari: a representative set of genomes of public health concern

Kalamari is a resource that supports genomic epidemiology and pathogen surveillance. It consists of representative genomes and common contaminants. Kalamari also contains a custom taxonomy and software for downloading and formatting the data.

Evolutionary and functional divergence of Sfx, a plasmid-encoded H-NS homolog, underlies the regulation of IncX plasmid conjugation

Conjugative plasmids are widespread among prokaryotes, highlighting their evolutionary success. Conjugation systems on most natural plasmids are repressed by default. The negative regulation of F-plasmid conjugation is partially mediated by the chromosomal nucleoid-structuring protein (H-NS). Recent bioinformatic analyses have revealed that plasmid-encoded H-NS homologs are widespread and exhibit high sequence diversity. However, the functional roles of most of these homologs and the selective forces driving their phylogenetic diversification remain unclear. In this study, we characterized the functionality and evolution of Sfx, a H-NS homolog encoded by the model IncX2 plasmid R6K. We demonstrate that Sfx, but not chromosomal H-NS, can repress R6K conjugation. Notably, we find evidence of positive selection acting on the ancestral Sfx lineage. Positively selected sites are located in the dimerization, oligomerization, and DNA-binding interfaces, many of which contribute to R6K repression activity-indicating that adaptive evolution drove the functional divergence of Sfx. We additionally show that Sfx can physically interact with various chromosomally encoded proteins, including H-NS, StpA, and Hha. Hha enhances the ability of Sfx to regulate R6K conjugation, suggesting that Sfx retained functionally important interactions with chromosomal silencing proteins. Surprisingly, the loss of Sfx does not negatively affect the stability or dissemination of R6K in laboratory conditions, reflecting the complexity of selective pressures favoring conjugation repression. Overall, our study sheds light on the functional and evolutionary divergence of a plasmid-borne H-NS-like protein, highlighting how these loosely specific DNA-binding proteins evolved to specifically regulate different plasmid functions.IMPORTANCEConjugative plasmids play a crucial role in spreading antimicrobial resistance and virulence genes. Most natural conjugative plasmids conjugate only under specific conditions. Therefore, studying the molecular mechanisms underlying conjugation regulation is essential for understanding antimicrobial resistance and pathogen evolution. In this study, we characterized the conjugation regulation of the model IncX plasmid R6K. We discovered that Sfx, a H-NS homolog carried by the plasmid, represses conjugation. Molecular evolutionary analyses combined with gain-of-function experiments indicate that positive selection underlies the conjugation repression activity of Sfx. Additionally, we demonstrate that the loss of Sfx does not adversely affect R6K maintenance under laboratory conditions, suggesting additional selective forces favoring Sfx carriage. Overall, this work underscores the impact of protein diversification on plasmid biology, enhancing our understanding of how molecular evolution affects broader plasmid ecology.

Exogenous plasmid capture to characterize tetracycline-resistance plasmids in sprouts obtained from retail in Germany

This study aimed to characterize antibiotic-resistance plasmids present in microorganisms from sprout samples using exogenous plasmid capture. Fresh mung bean sprouts were predominantly colonized by bacteria from the phyla Proteobacteria and Bacteroidetes. To capture plasmids, a plasmid-free Escherichia (E.) coli CV601 strain, containing a green fluorescent protein gene for selection, was used as the recipient strain in exogenous plasmid capture experiments. Transconjugants were selected on media containing cefotaxime or tetracycline antibiotics. While no cefotaxime-resistant transconjugants were obtained, 40 tetracycline-resistant isolates were obtained and sequenced by Illumina NextSeq short read and Nanopore MinION long read sequencing. Sequences were assembled using Unicycler hybrid assembly. Most of the captured long plasmids carried either the tet(A) or tet(D) resistance gene, belonged to the IncFI or IncFII replicon types, and were predicted as conjugative. While the smaller plasmids contained the tet(A) tetracycline resistance gene as well as additional quinolone (qnrS1), sulfonamide (sul1) and trimethoprim (dfrA1) resistance genes, the larger plasmids only contained the tet(D) resistance gene. An exception was the largest 192 kbp plasmid isolated, which contained the tet(D), as well as sulfonamide (sul1) and streptomycin (aadA1) resistance genes. The smaller plasmid was isolated from different sprout samples more often and showed a 100% identity in size (71,155 bp), while the 180 kbp plasmids showed some smaller or larger differences (in size between 157,683 to 192,360 bp). This suggested that the plasmids obtained from the similar sprout production batches could be clonally related. Nanopore MinION based 16S metagenomics showed the presence of Enterobacter (En.) cloacae, En. ludwigii, En. kobei, Citrobacter (C.) werkmanii, C. freundii, Klebsiella (K.) oxytoca and K. pneumonia, which have previously been isolated from fresh produce in Germany. These bacteria may harbor antibiotic resistance genes on plasmids that could potentially be transferred to similar genera. This study demonstrated that bacteria present in sprouts may act as the donors of antibiotic resistance plasmids which can transfer resistance to other bacteria on this product via conjugation.

Flies as carriers of antimicrobial resistant (AMR) bacteria in Nigerian hospitals: A workflow for surveillance of AMR bacteria carried by arthropod pests in hospital settings

The dissemination of antimicrobial resistant (AMR) bacteria by flies in hospitals is concerning as nosocomial AMR infections pose a significant threat to public health. This threat is compounded in low- and middle-income countries (LMICs) by several factors, including limited resources for sufficient infection prevention and control (IPC) practices and high numbers of flies in tropical climates. In this pilot study, 1,396 flies were collected between August and September 2022 from eight tertiary care hospitals in six cities (Abuja, Enugu, Kaduna, Kano, Lagos and Sokoto) in Nigeria. Flies were screened via microbiological culture and bacterial isolates were phenotypically and genetically characterised to determine carriage of clinically important antibiotic resistance genes (ARGs). Several clinically relevant ARGs were found in bacteria isolated from flies across all hospitals. blaNDM was detected in 8% of flies and was predominantly carried by Providencia spp. alongside clinically relevant Enterobacter spp, Escherichia coli and Klebsiella pneumoniae isolates, which all exhibited a multidrug resistant phenotype. mecA was detected at a prevalence of 6.4%, mostly in coagulase-negative Staphylococci (CoNS) as well as some Staphylococcus aureus, of which 86.8% were multidrug resistant. 40% of flies carried bacteria with at least one of the two ESBL genes tested (blaOXA-1 and blaCTX-M-15). This multi-site study emphasised that flies in hospital settings carry bacteria that are resistant to multiple classes of antibiotics, including both routinely used and reserve antibiotics. A greater understanding of the global clinical significance and burden of AMR attributable to insect pests is required.

The pivotal role of IncFIB(Mar) plasmid in the emergence and spread of hypervirulent carbapenem-resistant Klebsiella pneumoniae

The hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) poses a substantial challenge to the global health care. However, the mechanism behind its evolution and transmission remain elusive. Here, four virulence plasmid types were identified from 310 hv-CRKP isolates collected nationwide during 2017-2018, based on their aerobactin (iuc locus) lineage and IncFIB replicons. Notably, pIUC1-IncFIB(K)37 and pIUC1-IncFIB(Mar), representing two epidemic virulence plasmids in Asia and Europe, respectively, accounted for >90% of the hv-CRKP episodes. Analysis of 494 K. pneumoniae isolates (376 from 2010-2013; 118 from 2017-2018) and 2578 public K. pneumoniae genomes indicated the notable role of IncFIB(Mar) plasmids in the hv-CRKP emergence and spread. Conjugation assays showed the helper IncFIB(Mar) plasmid could efficiently transfer into a hypervirulent strain and uniquely retromobilize with pIUC1-IncFIB(K)37 back into CRKP. Thereafter, the IncFIB(Mar) plasmid either lost rapidly or recombined with pIUC1-IncFIB(K)37, generating the hybrid pIUC1-IncFIB(Mar) plasmid. Our findings elucidated formation, evolution, and dissemination trajectories of the two major hv-CRKP strains in different regions.

Multicenter evaluation of Fourier transform infrared (FTIR) spectroscopy as a first-line typing tool for carbapenemase-producing Klebsiella pneumoniae in clinical settings

Early use of infection control methods is critical for preventing the spread of antimicrobial resistance. Whole-genome sequencing (WGS) is considered the gold standard for investigating outbreaks; however, the turnaround time is usually too long for clinical decision-making and the method is also costly. The aim of this study was to evaluate the performance of Fourier transform infrared (FTIR) and artificial intelligence tools as a first-line typing tool for typing carbapenemase-producing Klebsiella pneumoniae (CPK) in the hospital setting. For this purpose, we analyzed 365 CPK isolates from two tertiary hospitals in Spain in parallel by applying unsupervised principal component analysis (PCA) and supervised algorithms (artificial neural network [ANN], support vector machine [SVM] linear, SVM radial basis function in the IR Biotyper software, and random forest in the Clover MSDAS software). Concordance with FTIR clustering considering the sequence type (ST) and the clonal cluster, obtained by cgMLST for reference purposes, was measured using the adjusted Wallace index (AWI), yielding values of 0.611 and 0.652, respectively. Different regions of the spectra were studied in relation to repeatability and reproducibility, and the polysaccharides region proved the best for FTIR differential analysis. The best results for accuracy were obtained using the ANN algorithm in the IR Biotyper software, with 80.5% of correct prediction. Regarding accuracy, the poorest results were obtained for isolates belonging to ST392 (55.5%) and the best results for ST307 (94.4%). The findings demonstrate the utility of the FTIR method as a rapid, inexpensive, first-line typing tool for detecting CPK, preserving WGS for confirmation and further characterization.

Insights into global antimicrobial resistance dynamics through the sequencing of enteric bacteria from U.S. international travelers

Antimicrobial resistance (AMR) is an urgent threat to public health, but gaps in surveillance limit the detection of emergent novel threats and knowledge about the global distribution of AMR genes. International travelers frequently acquire AMR organisms, and thus may provide a window into AMR dynamics in otherwise poorly monitored regions and environments. To assess the utility of travelers as global AMR sentinels, we collected pre- and post-travel stool samples from 608 travelers, which were screened for the presence of extended-spectrum beta-lactamase producing Enterobacterales, carbapenem-resistant Enterobacterales, and mcr-mediated colistin-resistant Enterobacterales. A total of 307 distinct AMR organisms were sequenced in order to determine genotypic patterns and their association with travel region and behavior. Travel-associated AMR organisms were overwhelmingly E. coli, which exhibited considerable phylogenetic diversity regardless of travel region. However, the prevalence of resistance genes varied by region, with bla CTX-M-55 and bla CTX-M-27 significantly more common in travelers returning from South America and South-Eastern Asia, respectively. Hybrid assembly and plasmid reconstruction revealed the genomic neighborhood of bla CTX-M-55 frequently matched a motif previously linked to animal populations. Contact with animals was also associated with virulence factors in acquired AMR organisms, including carriage of the ColV plasmid, a driver of avian pathogenic E. coli. We identified novel variants of the mcr-1 gene in strains acquired from Western Africa, highlighting the potential for traveler surveillance to detect emerging clinical threats. Ongoing efforts to track travel-acquired organisms could complement existing global AMR surveillance frameworks.

Quaternary Ammonium Compounds: A New Driver and Hidden Threat for mcr-1 Prevalence in Hospital Wastewater and Human Feces

The emergence of mobile colistin resistance gene mcr-1 has attracted global attention. The prevalence of mcr-1-positive Escherichia coli (MCRPEC) in humans largely decreased following the ban of colistin as an animal growth promoter in China. However, the prevalence of MCRPEC in the hospital environment and the relationship between disinfectants and mcr-1 remain unclear. We found that MCRPEC prevalence was low in the feces of healthy humans attending physical examinations in six hospitals (4.6%, 71/1532) but high in hospital wastewater (50.0%, 27/54). mcr-1 was mainly located on IncI2 (63.0% in wastewater and 62.0% in feces) and IncHI2 plasmids (18.5% in wastewater and 21.1% in feces). High similarity of the mcr-1 context and its carrying plasmids was observed in human and wastewater MCRPEC, with several isolates clustering together. The coexistence of the ESBL gene blaCTX-M with mcr-1 occurred in 19.7% of IncI2 plasmids. Notably, 60.0% of IncHI2 plasmids exhibited co-occurrence of mcr-1 with the disinfectant resistance gene (DRG) qacEΔ1, conferring resistance to quaternary ammonium compounds (QACs). We revealed that QACs, rather than the other two types of disinfectants─ortho-phthalaldehyde (OPA) and povidone-iodine (PVP-I)─select for plasmids carrying both qacEΔ1 and mcr-1 and elevate their conjugative transfer frequency. Monitoring of DRGs in MCRPEC and managing disinfectant use are urgently needed in healthcare settings to mitigate the spread of colistin resistance from hospital environments to inpatients.

zol and fai: large-scale targeted detection and evolutionary investigation of gene clusters

Many universally and conditionally important genes are genomically aggregated within clusters. Here, we introduce fai and zol, which together enable large-scale comparative analysis of different types of gene clusters and mobile-genetic elements, such as biosynthetic gene clusters (BGCs) or viruses. Fundamentally, they overcome a current bottleneck to reliably perform comprehensive orthology inference at large scale across broad taxonomic contexts and thousands of genomes. First, fai allows the identification of orthologous instances of a query gene cluster of interest amongst a database of target genomes. Subsequently, zol enables reliable, context-specific inference of ortholog groups for individual protein-encoding genes across gene cluster instances. In addition, zol performs functional annotation and computes a variety of evolutionary statistics for each inferred ortholog group. Importantly, in comparison to tools for visual exploration of homologous relationships between gene clusters, zol can scale to handle thousands of gene cluster instances and produce detailed reports that are easy to digest. To showcase fai and zol, we apply them for: (i) longitudinal tracking of a virus in metagenomes, (ii) performing population genetic investigations of BGCs for a fungal species, and (iii) uncovering evolutionary trends for a virulence-associated gene cluster across thousands of genomes from a diverse bacterial genus.

Antimicrobial resistant Enterobacterales of clinical importance in mute swans

Urban water environments, including canals, harbours and estuaries are susceptible to contamination with antimicrobials and drug-resistant bacteria through domestic and industrial wastewater discharges and storm water overflows. There is potential for wildlife using these waters to acquire and transmit drug-resistant bacteria and antimicrobial resistance genes (ARGs) of clinical importance. This study aimed to assess clinically important drug-resistant bacteria in urban waterfowl, particularly mute swans. Faecal samples were collected from 17 mute swans in the Greater Dublin Area, Ireland during July, August, October, and November of 2022. Samples were swabbed directly onto agars to select for carbapenem resistant, Extended-spectrum Beta-lactamase (ESBL)-producing, ciprofloxacin resistant and colistin resistant bacteria. Isolates identified by MALDI-TOF as Enterobacterales were tested for susceptibility to a panel of 16 antimicrobials and real-time PCR was employed to detect cefotaximase and carbapenemase genes (CRGs). Drug-resistant isolates were characterised by Whole Genome Sequencing (WGS), including long read sequencing for carbapenemase and mobile colistin resistance (mcr) gene-producing Enterobacterales isolates. Eleven of seventeen (65 %) swan samples were positive for the resistant organism(s) (n = 35), comprising Escherichia coli (n = 32; 82 %) and other Enterobacterales (n = 3). Twenty E. coli (63 %) produced ESBL, with 16/20 (80 %) identified as positive for blaCTX-M-group 1 enzymes, comprising CTX-M-15 (n = 13), CTX-M-55 (n = 2) and CTX-M-1 (n = 1) and 4/20 (20 %) positive for blaCTX-M-group 9 enzymes CTX-M-27 (n = 2) and CTX-M-9 (n = 2). Three E. coli isolates were phenotypically ertapenem resistant, one of which was an ST4450 isolate which carried plasmid encoded blaOXA-181 and blaCMY-141 with blaCTX-M-15 identified chromosomally. One colistin resistant E. coli bore the mcr-1 gene chromosomally. Bioinformatic analysis revealed high-risk pathogenic ESBL E. coli clones including ST38 (n = 3), ST69 (n = 3), and ST131 (n = 2). The study indicates mute swans are a reservoir for drug-resistant Enterobacterales and ARGs of clinical importance and may be a useful sentinel species for antimicrobial resistance (AMR) surveillance in wildlife.

Population genetic analysis of clinical Mycobacterium abscessus complex strains in China

Background

To explore the genetic characteristics of the Mycobacterium abscessus complex (MABC) population in China, given its rising clinical importance among nontuberculous mycobacteria.

Methods

We conducted population genetic analyses on 360 MABC genomes from China, focusing on core genome multilocus sequence typing (cgMLST), pan-genome characterization, population genetics, and antimicrobial resistance gene profiling.

Results

Our analysis identified 273 M. abscessus subsp. abscessus (MabA) and 87 M. abscessus subsp. massiliense (MabM) isolates, uncovering 68 sequence types (STs), with ST5 being the most common. cgMLST classified 33.3% of isolates into six dominant circulating clones (DCCs) and 49.4% into 59 genomic clusters at a threshold of 25 different alleles, including 18 international clusters linking Chinese isolates with seven other countries. The MABC pan-genome is open, with MabA exhibiting greater accessory gene diversity and higher gene turnover compared to MabM. Mobile genetic elements (MGEs), such as prophages and genomic islands, were prevalent across all genomes. 139 to 151 virulence factors (VFs) were identified per genome, with distinct accessory VFs in MabA and MabM affecting immune modulation and metabolism. Resistance gene profiling revealed ubiquitous mtrA, RbpA, and bla MAB, with MabA-specific erm(41) conferring resistance to macrolides and β-lactams. Common rrs and rrl gene mutations indicated widespread resistance to aminoglycosides and macrolides, while gyrA mutations suggested emerging fluoroquinolone resistance. An acquired erm(46) gene, likely obtained via phage-mediated horizontal gene transfer, was detected in one MabA strain.

Conclusion

This study provides key genetic insights into the dynamics of MABC in China. The widespread distribution of DCCs, high genomic clustering rates, open pan-genome, and distinct resistance patterns between MabA and MabM, along with MGEs, highlight the need for targeted surveillance and tailored therapies to address emerging challenges in MABC infections.

Genomic resistance in historical clinical isolates increased in frequency and mobility after the age of antibiotics

Antibiotic resistance is frequently observed shortly after the clinical introduction of an antibiotic. Whether and how frequently that resistance occurred before the introduction is harder to determine, as isolates could not have been tested for resistance before an antibiotic was discovered. Historical collections, like the British National Collection of Type Cultures (NCTC), stretching back to 1885, provide a window into this history. Here we match 1,817 sequenced high-quality genomes from the NCTC collection to their respective year of isolation to study resistance genes before and concurrent with the age of antibiotics. Concordant with previous work, we find resistance genes in both pathogens and environmental samples before the age of antibiotics. While generally rare before the introduction of an antibiotic, we find an associated increase in frequency with antibiotic introduction. Finally, we observe a trend of resistance elements becoming both increasingly mobile and nested within multiple mobile elements as time goes on. More broadly, our findings suggest that likely-functional antibiotic resistance genes were circulating in clinically relevant isolates before the age of antibiotics, but human usage is associated with increasing both their overall prevalence and mobility.

Plasmid and integron-associated antibiotic resistance in Escherichia coli isolated from domestic wastewater treatment plants

The rapid dissemination of antibiotic resistance genes (ARGs) represents a significant global threat, with wastewater treatment plants (WWTPs) playing an important role as reservoirs and propagation hubs. In this study, we performed whole-genome sequencing and bioinformatic analyses on eight multidrug-resistant Escherichia coli isolates previously obtained from domestic WWTPs in Costa Rica. We identified 61 ARGs (23 unique), with 40 located on plasmids, and 21 on chromosomal sequences, seven of which were within integrons. Several ARGs were associated with resistance to clinically and veterinary important antibiotics, including sulfamethoxazole/trimethoprim, beta-lactams, and tetracyclines. One hundred twenty-one virulence-associated genes (29 unique) were detected, with 16 located on plasmids. Notably, the presence of virulence factors such as ompT and hlyF genes alongside ARGs on plasmids underscores the transmissible pathogenic potential of WWTP-associated E. coli strains. These findings highlight the role of small domestic WWTPs in disseminating pathogenic and multidrug-resistant bacteria and their mobile genetic elements, emphasizing the need for further research to understand how these discharges impact aquatic environments.

Resistome phylodynamics of multidrug-resistant Shigella isolated from diarrheal patients

Multi-drug resistance (MDR) in Shigella continues to pose a significant public health challenge, particularly in developing countries. Recent advances in genomics strengthen the surveillance of MDR-pathogens and antimicrobial resistance (AMR) mediators. However, genome-based investigations into resistome dynamics in Shigella are limited, specifically in Bangladesh. Therefore, we investigated MDR-Shigella resistomes to evaluate their AMR transmission and phylodynamics. Clinical Shigella strains were screened for MDR phenotypes through susceptibility tests against 28 antibiotics from 10 different classes. Whole-genome sequencing (WGS) and bioinformatics approaches were performed to unveil the resistome dynamics: >500 global plasmid entities and >1,000 plasmid-mediated resistance gene clusters from global databases were included in this study. We identified 28 distinct antimicrobial resistance genes (ARGs) from nine antibiotic classes, with 75% originating from plasmids. Notably, two conjugative MDR plasmids included nearly all potential ARGs, conferring resistance to first-line drugs for shigellosis. Two third-generation cephalosporin-resistant [wubC-blaCTX-M-15-ISEcp1 and blaTEM-1] and two macrolide-resistant mobile genomic islands (GIs) [mphA-mrx-mph(R)A-IS6100 and mphE-msrE-IS482-IS6] had emerged in Shigella in Bangladesh. In addition, trimethoprim-aminoglycoside-streptothricin-sulfonamide-resistant dfrA1-sat1-aadA1 and aph3-dfrA14-aph6-sul2 were in conjugative plasmids in Bangladesh. The MDR plasmids and resistant GIs were phylogenetically relevant to Europe, USA, or China-derived isolates, indicating carry-over of the emerging ARGs from heavily industrialized countries and MSM-burdened (men who have sex with men) populations. The global burden of resistance GIs has increased sharply, especially after 2014. Emerging resistance mediators were most frequent (>80%) in human-associated Escherichia coli and Klebsiella pneumoniae. We infer ARGs horizontally propagate among Enteropathogens: informing treatment strategies and supporting policymakers in strengthening AMR-containment efforts utilizing the phylodynamics network.IMPORTANCEThe world is suffering from a high burden of MDR enteropathogens. Healthcare providers in low- and middle-income countries (LMICs) often face trouble finding effective drugs among the many antibiotics introduced in diarrheal treatment. Resistance-mediated drug inactivation is more rapid than the advent of new antimicrobials, leaving enteritis treatment on the edge. In Bangladesh, where one-third of users are self-prescribing antibiotics and thousands are dying due to resistance-related treatment failure, phylogenomic evidence of AMR transmission root is scarce. Therefore, investigating the resistomes of MDR-Shigella, the leading cause of diarrheal deaths in Bangladesh, is crucial. We identified several emerging resistance mediators and their phylogenetic links to global entities, which is significant for improving shigellosis treatment and enhancing AMR containment strategies. Understanding the MDR mechanism in Shigella will help physicians choose effective drugs and anticipate resistance-mediated changes in treatment approaches; the spatiotemporal phylodynamics of AMR mediators aid policymakers in setting effective checkpoints in the AMR transmission network.