Biology subjects

Brisse, S.

Publications and source records attributed to Brisse, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Modified Elek test improves in-vitro detection of diphtheria toxin

PurposeDiphtheria is caused by toxigenic strains of the Corynebacterium diphtheriae complex, mainly Corynebacterium diphtheriae and C. ulcerans. The diagnosis of diphtheria relies on detecting the diphtheria toxin (DT), for which Englers method of Eleks immunoprecipitation test is the gold standard. A recent optimization of Englers method was proposed by Melnikov and colleagues, showing higher sensitivity for C. ulcerans. The goal of our study was to test and adapt this optimized method, and to re-analyze apparent non-toxigenic tox gene bearing (NTTB) isolates from our collection. MethodsWe included 48 C. ulcerans, C. ramonii and C. diphtheriae isolates previously categorized as NTTB but for which no genetic explanation was found for the lack of DT expression. DT production was tested using Melnikovs method with further modifications made by us: i) increasing the antitoxin concentration; ii) using 5{degrees}C as the incubation temperature after 24h; and iii) modifying the layout of control and test strains on agar plates. Results35 of 38 C. ulcerans, 3 C. ramonii and 8 of 10 C. diphtheriae were found to be toxigenic. No genetic explanation was found regarding two non-toxigenic isolates (1 C. diphtheriae and 1 C. ulcerans), whereas for one C. diphtheriae, IS1132 was detected upstream of the tox gene. ConclusionOur modified implementation of Melnikovs Elek test improved our ability to detect diphtheria toxin production. Most isolates previously considered as NTTB but with no genetic explanation, were shown to be toxigenic using the novel method.

microbiology↗

bioRxiv2025

Pangenome structure and ecological adaptation in the Klebsiella pneumoniae species complex: insights from a geographically and time limited multi-habitat study

Klebsiella pneumoniae species complex (KpSC) members inhabit distinct ecological habitats, yet the diversity and adaptation of environmental KpSC populations remain underexplored. We investigated KpSC transmission, pangenome structure and diversity, and functional gene enrichment across four distinct habitats in Burgundy, France over one year. In total, 664 environmental samples were collected from an organic vegetable farm (n=329), an organic cattle farm (n=304) and wastewater treatment plants (WWTP; n=31), alongside 47 clinical isolates. KpSC was detected in 22.4% of environmental samples, most commonly in WWTP (83.9%), followed by vegetable farm (27.1%) and cattle farm (11.2%). A total of 336 isolates were collected and whole-genome sequenced. K. pneumoniae sensu stricto (phylogroup Kp1) was predominant (76%), followed by K. variicola subsp. variicola (phylogroup Kp3) (21%). Genomic analyses revealed substantial novel diversity, especially in environmental habitats (67 novel STs), with limited cross transmission but clear local persistence. Over 90% of environmental isolates lacked acquired antimicrobial resistance genes, whereas half of the clinical isolates exhibited a multi-drug resistance profile. Comparative pangenome analyses showed Kp1 possessed a larger and more diverse pangenome than Kp3. Human-associated populations (clinical and WWTP) shared similar pangenome structures, although clinical isolates exhibited an expanded accessory genome. Cattle farm isolates had the most restricted and distinct pangenome while vegetable farm isolates displayed the largest total genomic repertoire. Functional enrichment analysis highlighted Kp3s environmental adaptation via conserved functions linked to the phylogroup genetic background, such as metabolic and regulatory pathways, including nitrogen fixation genes. Contrarily, human-associated populations, especially Kp1 members, were enriched in acquired functions linked to the ecological context, including antimicrobial and metal resistance determinants and mobile genetic elements. These findings emphasize phylogroup- and ecological niche-driven pangenome contrasts in KpSC, contributing to explain the successful adaptation of Kp1 to multiple habitats, including human-related settings.

genomics↗

bioRxiv2025

Cumulative cgMLST provides increased discrimination of nested phylogenetic groups

BackgroundCore genome multilocus sequence typing (cgMLST) is a powerful method for bacterial strain genotyping. However, the size of the core genome decreases as the phylogenetic breadth of the target group increases, reducing discriminatory power. To overcome this discrimination/applicability tradeoff, here we developed a cumulative cgMLST approach, where sets of core loci conserved within nested phylogenetic entities are added. We illustrate this approach using the Klebsiella pneumoniae species complex (KpSC), for which a widely used cgMLST scheme (KpSC-cgMLST) comprises only 629 genes. MethodsWe created non-redundant cgMLST schemes for the individual species K. pneumoniae sensu stricto (Kpn-cgMLST scheme), and its multidrug resistant sublineages (SLs) SL147 and SL307. To extract core genes, we used 37,874 genome assemblies originating from over 80 countries worldwide. A methodology was set to filter redundant loci before importing them into the genotyping tool BIGSdb, where they were combined into schemes together with preexisting loci conserved at higher phylogenetic levels. The performance of the cumulative cgMLST schemes was evaluated on previously published datasets and on novel data from an inter-hospital outbreak of SL307. ResultsThe Kpn-cgMLST, SL147 and SL307 schemes comprise 2752, 852, and 947 additional loci, respectively. The mean allele call rate of the novel loci was >99% in the validation datasets. Compared to the KpSC scheme used alone, pairwise allelic distances among isolates increased on average 5.6-fold using the Kpn scheme, and further by 20% and 30% using the SL147 and SL307 schemes, respectively. We demonstrate the added value of this increased discriminatory power for epidemiological analyses and show nearly equal discrimination when compared to whole-genome single nucleotide polymorphisms analysis. ConclusionsThe cumulative cgMLST strategy combines broad phylogenetic applicability and nearly complete genotyping resolution, expanding the utility of this harmonized approach for genomic epidemiology.

microbiology↗

bioRxiv2025

Ciprofloxacin resistance in Klebsiella pneumoniae: phenotype prediction from genotype and global distribution of resistance determinants

BACKGROUNDCiprofloxacin resistant Klebsiella pneumoniae is common or emerging in many geographies, and knowledge of local resistance rates is important for empirical therapy. Whilst there are known K. pneumoniae ciprofloxacin resistance determinants, there is a lack of systematic data on the effect of determinants, alone and in combination, and there are no publicly accessible tools for predicting resistance from whole genome sequence data. METHODSThe KlebNET-GSP AMR Genotype-Phenotype Group aggregated a matched genotype-phenotype dataset of n=12,167 K. pneumoniae species complex (KpSC) isolates from 27 countries between 2001-2021. We developed a rules-based classifier to predict ciprofloxacin resistance by categorizing the number of quinolone resistance determining regions mutations in gyrA and parC, the number of plasmid-mediated quinolone resistance genes, and the presence/absence of aac(6')-Ib-cr (which can acetylate ciprofloxacin). Predictive performance was assessed using the discovery dataset, for which we re-phenotyped discrepant isolates; and validated using externally contributed datasets (n=7,030 KpSC isolates). RESULTSThe rules-based classifier predicted R vs S/I with categorical agreement, sensitivity, and specificity >96%, and major/very major error rates <4%. Performance was similar across diverse KpSC sources (human, animal, other), species, and intra-species lineages. External validation of the classifier yielded overall 93.12% categorical agreement [95% confidence interval (CI), 92.50-93.74%], 8.65% major errors [95% CI, 7.34-9.97%], and 6.20% very major errors [95% CI, 5.51-6.90%]. We implemented the classifier in Kleborate, a command-line tool that is integrated into the Pathogenwatch web platform. Using this to assess the global distribution of ciprofloxacin resistance determinants in KpSC genomes available in Pathogenwatch (n=31,319, from 109 countries between years 2000-2023), we observed a significant positive association between national quinolone consumption rates and predicted ciprofloxacin resistance (R2=0.20, p=0.004). CONCLUSIONS Ciprofloxacin resistance phenotypes can be reasonably predicted from genotypes, which is sufficient for informing surveillance. However, unexplained resistance remains and accuracy is insufficient for clinical applications. We demonstrate the value of aggregating genotype-phenotype data to explore resistance mechanisms and develop predictors, but highlight complexities in combining phenotype data from different assays and standards.

genomics↗

bioRxiv2025

Life identification number (LIN) codes for the genomic taxonomy of Corynebacterium diphtheriae strains

BackgroundCorynebacterium diphtheriae, which causes diphtheria, remains a public health concern especially in regions with low vaccination coverage. While advances in genomic typing, such as core-genome Multi-Locus Sequence Typing (cgMLST, based on 1305 genes), have improved our ability for strain identification, a standardized and stable genomic taxonomy is still lacking. This study aimed to establish a consistent classification and nomenclature for C. diphtheriae strains using cgMLST-based Life Identification Number (LIN) codes. MethodsComparing 1,665 genomes from C. diphtheriae and its closely related species C. belfantii and C. rouxii, we observed population-level genetic discontinuities in cgMLST profiles dissimilarities, and established hierarchical taxonomic levels based on optimal allelic difference thresholds. Ten-level LIN codes were defined, encompassing broad population structure subdivisions and fine-scale epidemiological levels. The LIN code system was implemented into the BIGSdb-Pasteur platform, and nicknames derived from the 7-loci MLST sequence types were given to sublineages and clonal groups. ResultscgMLST genetic thresholds were first defined at species (minimum of 1,240 allelic differences) and lineage levels (1,035 differences). Sublineages (SL), clonal groups (ClG), and genetic clusters (GC) were next defined with progressively finer allelic mismatch thresholds (500, 55, and 25 differences, respectively). A broad population diversity of C. diphtheriae was uncovered, with the distinction of >400 SLs and >1,000 GCs. For epidemiological purposes, five shallow-level thresholds (8, 4, 2 ,1, and 0 allelic mismatches were defined, completing the 10-level LIN code taxonomy. We illustrate LIN codes applicability to investigate the genetic diversity and transmission chains of relevant clusters, such as SL8 (the 1990s ex-USSR outbreak) or SL384 (involved in outbreaks in Yemen and Europe). ConclusionsThe cgMLST-based LIN code system provides a stable genomic taxonomy for strains of C. diphtheriae, C. rouxii and C. belfantii. By defining ten hierarchical levels of resolution, this system effectively captures its phylogenetic diversity, facilitating population biology research and epidemiological surveillance. The public availability of this system from the BIGSdb-Pasteur platform provides a standardized framework for diphtheria genomic epidemiology with potential to harmonize global surveillance of the resurgence of diphtheria.

microbiology↗

bioRxiv2024

Accurate genotyping of three major respiratory bacterial pathogens with ONT R10.4.1 long-read sequencing

High-throughput massive parallel sequencing has significantly improved bacterial pathogen genomics, diagnostics, and epidemiology. Despite its high accuracy, short-read sequencing struggles with complete genome reconstruction and assembly of extrachromosomal elements such as plasmids. Long-read sequencing with Oxford Nanopore Technologies (ONT) presents an alternative that offers benefits like real-time sequencing and cost-efficiency, particularly useful in resource-limited settings. However, the higher error rates of ONT have so far limited its application in high-precision genomic typing. The recent release of ONTs R10.4.1 chemistry, with significantly improved raw read accuracy (Q20+), offers a potential solution to this problem. The aim of this study was to evaluate the performance of ONTs latest chemistry for bacterial genomic typing against the gold standard Illumina technology, focusing on three respiratory pathogens of public health importance, Klebsiella pneumoniae, Bordetella pertussis, and Corynebacterium diphtheriae, and their related species. Using the Rapid Barcoding Kit V14, we generated and analyzed genome assemblies with different basecalling tools and models, at different simulated depths of coverage. ONT assemblies were compared to the Illumina reference for completeness and core genome multilocus sequence typing (cgMLST) accuracy (number of allelic mismatches). Our results show that genomes obtained from raw data basecalled with Dorado (with both simplex and duplex reads) SUP v0.7.1, assembled with Flye, and with a minimum coverage depth of 30x, optimized the accuracy for all bacterial species tested. The error rates were consistently below 1% of each cgMLST scheme, indicating that ONT R10.4.1 data is suitable for high-resolution genomic typing applied to outbreak investigations and public health surveillance.

genomics↗

bioRxiv2024

A genome-wide One Health study of Klebsiella pneumoniae in Norway reveals overlapping populations but few recent transmission events across reservoirs

Members of the Klebsiella pneumoniae species complex (KpSC) are opportunistic pathogens that cause severe and difficult-to-treat infections. KpSC are common in non-human niches, but the clinical relevance of these populations is disputed. Utilising 3,255 whole-genome sequenced isolates from human, animal and marine sources collected during 2001-2020 in Norway, we showed the KpSC populations in different niches were distinct but overlapping. Notably, human infection isolates showed greatest connectivity with each other, followed by isolates from human carriage, pigs, and bivalves. Nearly 5% of human infection isolates had close relatives ([≤]22 substitutions) amongst animal and marine isolates, despite temporally and geographically distant sampling of these sources. Infection prevention measures are essential to limit transmission within human clinical settings and reduce disease burden. However, as colonisation often precedes infection, preventing transmission that leads to colonisation, e.g. transmission between animals and humans in the community, and in the food chain, could also be beneficial.

microbiology↗

bioRxiv2024

Genomic Epidemiology and Microevolution of the Zoonotic Pathogen Corynebacterium ulcerans

Corynebacterium ulcerans is an emerging zoonotic pathogen that belongs to the Corynebacterium diphtheriae (Cd) species complex (CdSC), and that causes diphtheria-like infections in humans. Our understanding of the transmission, phylogeography and evolution of C. ulcerans remains limited, in part due to the lack of a standardized genomic epidemiology toolkit. The aim of this work was to develop a core genome multi-locus sequence typing (cgMLST) scheme for high-resolution genotyping and classification of C. ulcerans strains, and to explore transmission, spatial spread and genomic evolution among 582 C. ulcerans isolates from sporadic clinical cases and reported case clusters. The cgMLST scheme combines 1,628 loci with highly reproducible allele calls and shows high strain subtyping resolution. We demonstrate its utility for capturing population structure by defining sublineages (SL, maximum 940 allele differences) and clonal groups (CG, 194 allele differences, AD) and for epidemiological surveillance by defining genetic clusters, i.e., previously undetected chains of transmission (25 AD). Genetic clusters correspond to cryptic and case clusters that were associated with specific geographical regions within France. Major C. ulcerans sublineages (SL325, SL331, SL339) and clonal groups (CG325, CG331, CG583) showed strong associations with diphtheria toxin variants and tox-carrying prophages or other genetic elements. The evolutionary dynamics of tox gene presence or absence varied sharply among clonal groups. The cgMLST scheme is publicly available (https://bigsdb.pasteur.fr/diphtheria) and provides a common framework for investigating the ecology, evolution and variations in virulence among C. ulcerans strains. The implementation of a standardized high-resolution genotyping method will also facilitate the tracing of C. ulcerans transmission and spread across hosts and from local to global spatial scales.

microbiology↗

bioRxiv2024

A metabolic atlas of the Klebsiella pneumoniae species complex reveals lineage-specific metabolism that supports persistent co-existence of diverse lineages

The Klebsiella pneumoniae species complex inhabits a wide variety of hosts and environments, and is a major cause of antimicrobial resistant infections. Genomics has revealed the population comprises multiple species/subspecies and hundreds of distinct co-circulating sub-lineages that are associated with distinct gene complements. A substantial fraction of the pan-genome is predicted to be involved in metabolic functions and hence these data are consistent with metabolic differentiation as a driver of population structure. However, this has so far remained unsubstantiated because in the past it was not possible to explore metabolic variation at scale. Here we used a combination of comparative genomics and high-throughput genome-scale metabolic modelling to systematically explore metabolic diversity across the K. pneumoniae species complex (n=7,835 genomes). We simulated growth outcomes for each isolate using carbon, nitrogen, phosphorus and sulfur sources under aerobic and anaerobic conditions (n=1,278 conditions per isolate). We showed that the distributions of metabolic genes and growth capabilities are structured in the population, and confirmed that sub-lineages exhibit unique metabolic profiles. In vitro co-culture experiments demonstrated reciprocal commensalistic cross-feeding between sub-lineages, effectively extending the range of conditions supporting individual growth. We propose that these substrate specialisations promote the existence and persistence of co-circulating sub-lineages by reducing nutrient competition and facilitating commensal interactions via negative frequency-dependent selection. Our findings have implications for understanding the eco-evolutionary dynamics of K. pneumoniae and for the design of novel strategies to prevent opportunistic infections caused by this World Health Organization priority antimicrobial resistant pathogen.

microbiology↗

bioRxiv2024

No innocent bystanders: pertussis vaccination epitomizes evolutionary parallelisms between Bordetella parapertussis and B. pertussis

Pathogens adapting to the human host and to vaccination-induced immunity may follow parallel evolutionary paths. Bordetella parapertussis (Bpp) contributes significantly to the burden of whooping cough (pertussis), shares vaccine antigens with Bordetella pertussis (Bp), and both pathogens are phylogenetically related and ecological competitors. Bp vaccine antigen-coding genes have accumulated variation, including pertactin disruptions, after introduction of acellular vaccines in the 1990s. We aimed to evaluate evolutionary parallelisms in Bpp, even though pertussis vaccines were designed against Bp. We investigated the temporal evolution of Bpp sublineages, by sequencing 242 Bpp isolates collected in France, the USA and Spain between 1937 and 2019, spanning pre-vaccine and two vaccines eras. We estimated the evolutionary rate of Bpp at 2.12x10-7 substitutions per site{middle dot}year-1, with a most recent common ancestor of all sequenced isolates around year 1877, and found that pertactin deficiency in Bpp was driven by 18 disruptive mutations, including deletion prn:{Delta}G-1895 estimated to have occurred around 1998 and observed in 73.8% (149/202) of post-2007 isolates. In addition, we detected two mutations in the bvgA-fhaB intergenic region (controlling expression of the master transcriptional regulator BvgA and the filamentous hemagglutinin), that became fixed in the early 1900s. Our findings suggest early adaptation of Bpp to humans through modulation of the bvgAS regulon, and a rapid adaptation through the loss of pertactin expression, representing a late evolutionary parallelism concomitant with acellular vaccination against whooping cough. IMPORTANCEVaccination against Bordetella pertussis (Bp) has strongly affected the recent evolution of this main agent of whooping cough. Whether it may have done so co-incidentally on Bordetella parapertussis (Bpp), which is genetically and ecologically very similar to Bp, has not been described in detail. Our findings show striking evolutionary parallelisms of Bpp with Bp, including early changes in a critical regulatory region, and strong evidence of adaptation to vaccine-driven population immunity, even though whooping cough vaccines were not designed explicitly against Bpp. The rapid populational loss of pertactin in countries where acellular pertussis vaccines are used may also reduce protection by vaccination against Bpp, the second agent of whooping cough.

microbiology↗

bioRxiv2024

Genomic and functional analysis of rmp locus variants in Klebsiella pneumoniae

AbstractO_ST_ABSBackgroundC_ST_ABSKlebsiella pneumoniae is an opportunistic pathogen and a leading cause of healthcare-associated infections in hospitals, which are frequently antimicrobial resistant (AMR). Exacerbating the public health threat posed by K. pneumoniae, some strains also harbor additional hypervirulence determinants typically acquired via mobile genetic elements such as the well-characterised large virulence plasmid KpVP-1. The rmpADC locus is considered a key virulence feature of K. pneumoniae and is associated with upregulated capsule expression and the hypermucoid phenotype, which can enhance virulence by contributing to serum resistance. Typically such strains have been susceptible to all antimicrobials besides ampicillin, however the recent emergence of AMR hypermucoid strains is concerning. MethodsHere, we investigate the genetic diversity, evolution, mobilisation and prevalence of rmpADC, in a dataset of 14000 genomes from isolates of the Klebsiella pneumoniae species complex, and describe the RmST virulence typing scheme for tracking rmpADC variants for the purposes of genomic surveillance. Additionally, we examine the functionality of representatives for variants of rmpADC introduced into a mutant strain lacking its native rmpADC locus. ResultsThe rmpADC locus was detected in 7% of the dataset, mostly from genomes of K. pneumoniae and a very small number of K. variicola and K. quasipneumoniae. Sequence variants of rmpADC grouped into five distinct lineages (rmp1, rmp2, rmp2A, rmp3 and rmp4) that corresponded to unique mobile elements, and were differentially distributed across different populations (i.e. clonal groups) of K. pneumoniae. All variants were demonstrated to produce enhanced capsule production and hypermucoviscosity. ConclusionThese results provide an overview of the diversity and evolution of a prominent K. pneumoniae virulence factor and support the idea that screening for rmpADC in K. pneumoniae isolates and genomes is valuable to monitor the emergence and spread of hypermucoid K. pneumoniae, including AMR strains.

genomics↗

bioRxiv2024

Phenotypic and genomic changes in enteric Klebsiella populations during long-term ICU patient hospitalization: The role of RamR regulation

Acquired antimicrobial resistance and metabolic changes are central for bacterial host adaptation during the long-term hospitalization of patients. We aimed to analyze the genomic and phenotypic evolution of enteric Klebsiella populations in long-term intensive care unit (ICU) patients. Weekly rectal swabs were prospectively collected from all patients admitted to the ICU in a teaching hospital from December 2018 to February 2019. The inclusion criterion for patients was hospitalization for more than 15 days in the ICU without any history of hospitalization or antibiotic treatment for the three months prior to admission. Among them, enteric Klebsiella pneumoniae species complex (KpSC) populations were detected. For each isolate, extensive antimicrobial resistance profiles were determined using the disk diffusion method, and the whole genome was sequenced using an Illumina platform. In silico typing methods, such as multilocus sequence typing (MLST), core-genome MLST, SNP typing, resistome characterization and mutation point detection, were applied. During the study period, 471 patients were admitted to ICUs. Among them, 21 patients met the inclusion criteria, and only five patients (24%) carried unique and distinct KpSC populations during two to ten weeks in the gut that as detected at admission and excluding acquisition during the ICU stay. One patient showed a rare ST1563 K. variicola persistent carriage for seven consecutive weeks, which displayed important antimicrobial resistance phenotype changes in the two last weeks. In-depth in silico characterization and RNA sequencing of these strains revealed a mutation within the ramR transcriptional regulator resulting in overexpression of the ramA regulator and decreased expression of acrR. These modifications are implicated in multidrug resistance, biliary salt tolerance and other bacterial functions. This study revealed the importance of endogenous colonization of KpSC populations in the gut throughout the patients long-term ICU stay and highlighted the role of ramR regulation in microbial adaptation. Author summaryKlebsiella variicola belongs to a large bacterial complex named the Klebsiella pneumoniae species complex (KpSC). These bacteria are largely involved in nosocomial infection and are able to colonize human gut microbiota during hospitalization and/or develop antimicrobial resistance during the hospital stay. In this work, we aimed to determine the prevalence at admission and adaptation of persistent KpSC populations in the gut of long-term ICU patients. Among 471 patients admitted, 21 were hospitalized for more than 15 days, and 5 carried a unique and distinct endogenous KpSC. K. variicola was detected in two of the five patients, and antibiotic resistance was detected during long-term hospitalization in these patients. One K. variicola strain became cross-resistant to chloramphenicol, quinolones and tigecycline after the seventh week of hospitalization. In silico analyses revealed the persistence of a rare ST 1563 K. variicola population with a mutation in the ramR transcriptional regulator, which controls RND efflux pump expression and antibiotic efflux. This mutation also impacts tolerance to biliary salts and probably biofilm formation. In conclusion, a mutation in an important transcriptional regulator, ramR, could be involved in not only antimicrobial resistance but also facilitate persistent K. variicola colonization.

microbiology↗

bioRxiv2024

Diversity, functional classification and genotyping of SHV β-lactamases in Klebsiella pneumoniae

Interpreting phenotypes of blaSHV alleles in Klebsiella pneumoniae genomes is complex. While all strains are expected to carry a chromosomal copy conferring resistance to ampicillin, they may also carry mutations in chromosomal blaSHV alleles or additional plasmid-borne blaSHV alleles that have extended-spectrum {beta}-lactamase (ESBL) activity and/or {beta}-lactamase inhibitor (BLI) resistance activity. In addition, the role of individual mutations/amino acid changes is not completely documented or understood. This has led to confusion in the literature and in antimicrobial resistance (AMR) gene databases (e.g., NCBIs Reference Gene Catalog and the {beta}-lactamase database (BLDB)) over the specific functionality of individual SHV protein variants. Therefore, identification of ESBL-producing strains from K. pneumoniae genome data is complicated. Here, we reviewed the experimental evidence for the expansion of SHV enzyme function associated with specific amino-acid substitutions. We then systematically assigned SHV alleles to functional classes (wildtype, ESBL, BLI-resistant) based on the presence of these mutations. This resulted in the re-classification of 37 SHV alleles compared with current assignments in NCBIs Reference Gene Catalog and/or BLDB (21 to wildtype, 12 to ESBL, 4 to BLI-resistant). Phylogenetic and comparative genomic analyses support that; i) SHV-1 (encoded by blaSHV-1) is the ancestral chromosomal variant; ii) ESBL and BLI-resistant variants have evolved multiple times through parallel substitution mutations; iii) ESBL variants are mostly mobilised to plasmids; iv) BLI-resistant variants mostly result from mutations in chromosomal blaSHV. We used matched genome-phenotype data from the KlebNET-GSP Genotype-Phenotype Group to identify 3,999 K. pneumoniae isolates carrying one or more blaSHV alleles but no other acquired {beta}-lactamases, with which we assessed genotype-phenotype relationships for blaSHV. This collection includes human, animal, and environmental isolates collected between 2001 to 2021 from 24 countries across six continents. Our analysis supports that mutations at Ambler sites 238 and 179 confer ESBL activity, while most omega-loop substitutions do not. Our data also provide direct support for wildtype assignment of 67 protein variants, including eight that were noted in public databases as ESBL. We reclassified these eight variants as wildtype, because they lack ESBL-associated mutations, and our phenotype data support susceptibility to 3GCs (SHV-27, SHV-38, SHV-40, SHV-41, SHV-42, SHV-65, SHV-164, SHV-187). The approach and results outlined here have been implemented in Kleborate v2.4.1 (a software tool for genotyping K. pneumoniae from genome assemblies), whereby known and novel blaSHV alleles are classified based on causative mutations. Kleborate v2.4.1 was also updated to include ten novel protein variants from the KlebNET-GSP dataset and all alleles in public databases as of November 2023. This study demonstrates the power of sharing AMR phenotypes alongside genome data to improve understanding of resistance mechanisms. Impact statementSince every K. pneumoniae genome has an intrinsic SHV {beta}-lactamase and may also carry additional mobile forms, the correct interpretation of blaSHV genes detected in genome data can be challenging and can lead to K. pneumoniae being misclassified as ESBL-producing. Here, we use matched K. pneumoniae genome and drug susceptibility data contributed from dozens of studies, together with systematic literature review of experimental evidence, to improve our understanding of blaSHV allele variation and mapping of genotype to phenotype. This study shows the value of coordinated data sharing, in this case via the KlebNET-GSP Genotype-Phenotype Group, to improve our understanding of the evolutionary history and functionality of blaSHV genes. The results are captured in an open-source AMR dictionary utilised by the Kleborate genotyping tool, that could easily be incorporated into or used to update other tools and AMR gene databases. This work is part of the wider efforts of the KlebNET-GSP group to develop and support a unified platform tailored for the analysis and interpretation of K. pneumoniae genomes by a wide range of stakeholders. Data summaryBlaSHV allele sequences and class assignments are distributed with Kleborate, v2.4.1, DOI:10.5281/zenodo.10469001. Table S1 provides a summary of blaSHV alleles, including primary accessions, class-modifying mutations, and supporting evidence for class assignments that differ from NCBIs Reference Gene Catalog or BLDB. Whole genome sequence data are publicly available as reads and/or assemblies, individual accessions are given in Table S2; corresponding genotypes and antibiotic susceptibility phenotypes and measurements are available in Tables S3 and S4, respectively.

genomics↗

bioRxiv2024

Bacterial strain nomenclature in the genomic era: Life Identification Numbers using a gene-by-gene approach

Unified strain taxonomies are needed for the epidemiological surveillance of bacterial pathogens and international communication in microbiological research. Core genome multilocus sequence typing (cgMLST) holds great promise for standardized high-resolution strain genotyping. However, this approach faces challenges including classification instability and disconnection of new nomenclature from widely adopted classical MLST identifiers. This essay discusses the cgMLST-based Life Identification Number (LIN) method, recently proposed as a stable multilevel strain taxonomy system applicable to most bacterial pathogens. We describe how LIN codes are implemented and used in practice for precise strain definitions and epidemiological tracking. Glossary Multilocus sequence typing (MLST)A genotyping method applied mostly to microbial strains to study population structure and epidemiology, based on comparing the nucleotide sequences of a small number (typically seven) of housekeeping protein-coding genes. In MLST, allele numbers are assigned to each sequence variant (allele) of a given gene. The MLST genotype of a bacterial strain is defined by the combination of the allele numbers observed at the genes that are included in the genotyping scheme. A sequence type (ST) is assigned to each unique combination of alleles, called an MLST profile. MLST was invented in 1998 and became a de-facto standard taxonomy of bacterial strains, albeit at low resolution. Core genome MLSTAn extension of MLST that analyzes sequence variation across hundreds to thousands of conserved (core) genes, shared by all strains of a species, providing higher resolution typing for genomic epidemiology and evolutionary studies. cgMLST schemes typically comprise 2000 to 4000 genes, depending on the genome size and genetic variation (in terms of presence/absence of genes) within bacterial species. A core genome sequence type (cgST) can be assigned to unique cgMLST profiles, i.e., a unique combination of cgMLST allelic numbers. Whole Genome Sequencing (WGS)A method that determines the complete DNA sequence of an organisms genome in a single process, providing comprehensive information for comparative genetic analyses based on cgMLST or other analytic methods. Single Nucleotide Polymorphisms (SNPs)Variations at a single base position in the DNA sequence among individuals isolates, strains or species, used as genetic markers for studying for example, evolutionary relationships or strain identity. Average nucleotide identity (ANI)A measure of genomic similarity between two organisms, calculated as the average percentage of identical nucleotides in orthologous genomic regions; commonly used to assess species-level relatedness in prokaryotes. TaxonomyHere, we apply the word taxonomy to bacterial strains as a system of classifying, naming and identifying strains based on shared genetic characteristics as defined by e.g., cgMLST.

microbiology↗

bioRxiv2024

Triplex real-time PCR ZKIR-T assay for simultaneous detection of the Klebsiella pneumoniae species complex and identification of K. pneumoniae sensu stricto

Klebsiella pneumoniae species complex (KpSC) members, including the most important species K. pneumoniae (phylogroup Kp1 of the KpSC), are important opportunistic pathogens which display increasing rates of antimicrobial resistance worldwide. As they are widespread in food and the environment, there is a need for fast, sensitive and reliable methods to detect KpSC members in complex matrices. Previously, the ZKIR real-time PCR assay was developed to detect all KpSC members without distinction. Given that Kp1 is the clinically most significant phylogroup of the KpSC, here we aimed to simultaneously identify Kp1 while detecting all KpSC members. Three TaqMan probes were developed and used: the zkir P1 probe to detect phylogroups Kp1 to Kp5 and Kp7; the zkir P2 probe to detect phylogroup Kp6; and the Kp1 probe to specifically identify this phylogroup. The new assay was tested on a total of 95 KpSC and 19 non-KpSC strains from various sources, representing the different phylogroups as defined by whole genome sequencing. The results showed almost complete specificity, as the expected PCR results were obtained for 112 (98%) strains. The new triplex real-time PCR assay, called ZKIR-T, enables detection of all KpSC taxa while discriminating Kp1, which will be useful for rapid screening and to focus downstream analyses on chosen phylogroups of the KpSC. ImportanceThe pathogens of the Klebsiella pneumoniae species complex are widespread in food and animals and are amongst the main pathogens responsible for multidrug resistant infections in humans. In this study, we developed a highly sensitive detection assay that enables detection of this group of bacteria, with the simultaneous identification of the most common and clinically important species. This triplex one-reaction assay was shown to be highly sensitive and precise, enabling fast screening of varied samples for the presence of KpSC and K. pneumoniae sensu stricto.

microbiology↗

bioRxiv2023

A validated pangenome-scale metabolic model for the Klebsiella pneumoniae species complex

The Klebsiella pneumoniae Species Complex (KpSC) is a major source of nosocomial infections globally with high rates of resistance to antimicrobials. Consequently, there is growing interest in understanding virulence factors and their association with cellular metabolic processes for developing novel anti-KpSC therapeutics. Phenotypic assays have revealed metabolic diversity within the KpSC, but metabolism research has been neglected due to experiments being difficult and cost-intensive. Genome-scale metabolic models (GSMMs) represent a rapid and scalable in silico approach for exploring metabolic diversity, which compiles genomic and biochemical data to reconstruct the metabolic network of an organism. Here we use a diverse collection of 507 KpSC isolates, including representatives of globally distributed clinically-relevant lineages, to construct the most comprehensive KpSC pan-metabolic model to-date, KpSC pan v2. Candidate metabolic reactions were identified using gene orthology to known metabolic genes, prior to manual curation via extensive literature and database searches. The final model comprised a total of 3,550 reactions, 2,403 genes and can simulate growth on 360 unique substrates. We used KpSC pan v2 as a reference to derive strain-specific GSMMs for all 507 KpSC isolates, and compared these to GSMMs generated using a prior KpSC pan-reference (KpSC pan v1) and two single-strain references. We show that KpSC pan v2 includes a greater proportion of accessory reactions (8.8%) than KpSC pan v1 (2.5%). GSMMs derived from KpSC pan v2 also result in more accuracy growth predictions than those derived from other references in both aerobic (median accuracy = 95.4%) and anaerobic (median accuracy = 78.8%). KpSC pan v2 also generates more accurate growth predictions, with high median accuracies of 95.4% (aerobic, n=37 isolates) and 78.8% (anaerobic, n=36 isolates) for 124 matched carbon substrates. KpSC pan v2 is freely available at https://github.com/kelwyres/KpSC-pan-metabolic-model, representing a valuable resource for the scientific community, both as a source of curated metabolic information and as a reference to derive accurate strain-specific GSMMs. The latter can be used to investigate the relationship between KpSC metabolism and traits of interest, such as reservoirs, epidemiology, drug resistance or virulence, and ultimately to inform novel KpSC control strategies. Significance as a BioResource to the communityKlebsiella pneumoniae and its close relatives in the K. pneumoniae Species Complex (KpSC) are priority antimicrobial resistant pathogens that exhibit extensive genomic diversity. There is growing interest in understanding KpSC metabolism, and genome scale metabolic models (GSMMs) provide a rapid, scalable option for exploration of whole cell metabolism plus phenotype prediction. Here we present a KpSC pan-metabolic model representing the cellular metabolism of 507 diverse KpSC isolates. Our model is the largest and most comprehensive of its kind, comprising >2,400 genes associated with >3,500 metabolic reactions, plus manually curated evidence annotations. These data alone represent a key knowledge resource for the Klebsiella research community; however, our models greatest impact lies in its potential for use as a reference from which highly accurate strain-specific GSMMs can be derived to inform in depth strain-specific and/or large-scale comparative analyses. Data summaryO_LIKlebsiella pneumoniae species complex (KpSC) pan v2 metabolic model available at https://github.com/kelwyres/KpSC-pan-metabolic-model. C_LIO_LIAll KpSC isolate whole genome sequences used in this work were reported previously and are available under Bioprojects PRJEB6891, PRJNA351909, PRJNA493667, PRJNA768294, PRJNA253462, PRJNA292902 and PRJNA391323. Individual accessions listed in Table S1. C_LIO_LIStrain-specific GSMMs used for comparative analyses (deposited in Figshare - 10.6084/m9.figshare.24871914), plus their associated MEMOTE reports (indicates completeness and annotation quality), reaction and gene presence-absence matrices across all isolates. C_LIO_LIGrowth phenotype predictions derived from strain-specific GSMMs are available in Table S4. C_LIO_LIBinarised Biolog growth phenotype data for n=37 isolates (plates PM1 and PM2, aerobic and anaerobic conditions) are available in Tables S6 & S7. C_LIO_LIAdditional growth assay data for six substrates not included on Biolog plates PM1 and PM2 (deposited in Figshare - 10.6084/m9.figshare.24871914). C_LI

genomics↗

bioRxiv2023

A global Corynebacterium diphtheriae genomic framework sheds light on current diphtheria reemergence

BackgroundDiphtheria, caused by Corynebacterium diphtheriae, reemerges in Europe since 2022. Genomic sequencing can inform on transmission routes and genotypes of concern, but currently, no standard approach exists to detect clinically important genomic features and to interpret emergence in the global C. diphtheriae population framework. MethodsWe developed the bioinformatics pipeline DIPHTOSCAN (available at https://gitlab.pasteur.fr/BEBP/diphtoscan) to extract from genomes of Corynebacteria of the diphtheriae species complex, medically relevant features including tox gene presence and disruption. We analyzed 101 human C. diphtheriae isolates collected in 2022 in metropolitan and overseas France (France-2022). To define the population background of this emergence, we sequenced 379 additional isolates (mainly from France, 2018-2021) and collated 870 publicly-available genomes. ResultsThe France-2022 isolates comprised 45 tox-positive (44 toxigenic) isolates, mostly imported, belonging to 10 sublineages (<500 distinct core genes). The global dataset comprised 245 sublineages and 33.9% tox- positive genomes, with DIPHTOSCAN predicting non-toxigenicity in 16.0% of these. 12% of the global isolates, and 43.6% of France-2022 ones, were multidrug resistant. Convergence of toxigenicity with penicillin and erythromycin resistance was observed in 2 isolates from France-2022. Phylogenetic lineages Gravis and Mitis contrasted strikingly in their pathogenicity-associated genes. ConclusionsThis work provides a bioinformatics tool and global population framework to analyze C. diphtheriae genomes, revealing important heterogeneities in virulence and resistance features. Emerging genotypes combining toxigenicity and first-line antimicrobial resistance represent novel threats. Genomic epidemiology studies of C. diphtheriae should be intensified globally to improve understanding of reemergence and spatial spread.

microbiology↗

bioRxiv2023

Corynebacterium of the diphtheriae complex in companion animals: clinical and microbiological characterization of 64 cases from France

ObjectivesCorynebacteria of the diphtheriae complex (Cdc) can cause diphtheria in humans and have been reported from companion animals. We aimed to describe animal infection cases caused by Cdc isolates. Methods18 308 animals (dogs, cats, horses and small mammals) with rhinitis, dermatitis, non-healing wounds and otitis were sampled in metropolitan France (August 2019 to August 2021). Data on symptoms, age, breed, and the administrative region of origin were collected. Cultured bacteria were analyzed for tox gene presence, for production of the diphtheria toxin, for antimicrobial susceptibility, and genotyped by multilocus sequence typing. ResultsC. ulcerans was identified in 51 cases, 24 of which were toxigenic. Rhinitis was the most frequent presentation (18/51). Eleven cases (6 cats, 4 dogs, 1 rat) were mono-infections. Large breed dogs, especially German Shepherds (9 of 28 dogs; p < 0.00001) were overrepresented. C. ulcerans isolates were susceptible to all tested antibiotics. tox-positive C. diphtheriae was identified in 2 horses. Last, 11 infections cases (9 dogs, 2 cats; mostly chronic otitis, and 2 sores) had tox-negative C. rouxii, a recently defined species. C. rouxii and C. diphtheriae isolates were susceptible to most antibiotics tested, and almost all of these infections were polymicrobial. ConclusionsMonoinfections with C. ulcerans point towards a primary pathogenic potential to animals. C. ulcerans represents an important zoonotic risk, and C. rouxii may represent a novel zoonotic agent. This case series provides novel clinical and microbiological data on Cdc infections, and underlines the need for management of animals and their human contacts. ImportanceWe report on the occurrence, clinical and microbiological characteristics of infections caused by members of the Corynebacteria of the diphtheriae complex (Cdc) in companion animals. This is the first study based on the systematic analysis of a very large animal cohort (18 308 samples), which provides data on the frequency of Cdc isolates in various types of clinical samples from animals. Awareness of this zoonotic bacterial group remains low among veterinarians and veterinary laboratories, among which it is often considered a commensal bacteria of animals. We suggest that in case of Cdc detection in animals, the veterinary laboratories should be encouraged to send the samples to a reference laboratory for analysis of the presence of the tox gene. This work is relevant to the development of guidelines in case of Cdc infections in animals, and underlines their public health relevance given the zoonotic transmission risk.

microbiology↗