Biology subjects

Kathariou, S.

Publications and source records attributed to Kathariou, S..

3 recordsLinked to original sources

bioRxiv2026

Novel, highly divergent clones in Listeria monocytogenes serotype 4b in North America: Sublineages 782 and 1039, members of the hypervirulent clonal complex 2

Listeria monocytogenes is a Gram-positive bacterial foodborne pathogen responsible for the severe illness listeriosis. Of the 14 L. monocytogenes serotypes, serotype 4b is a major contributor to human listeriosis and encompasses all four leading hypervirulent clonal complexes (CCs), including the ancient, ubiquitous CC2. CC2 is globally dominated by sublineage (SL) 2, responsible for most human CC2-associated cases. Here we describe two other CC2 SLs, SLs 782 and 1039. These SLs are newly recognized, having been reported only since 2002, and to date are encountered exclusively in North America. Phylogenetic analysis revealed that they are strikingly divergent from each other as well as from SL2. SL782 and SL1039 have been implicated in human listeriosis and have also been repeatedly isolated from surface water and wildlife in North America, with several of these environmental strains exhibiting high genomic similarity ([≤]7 core genome allelic mismatches) to strains from human listeriosis. They share an unusual resistance profile towards a panel of Listeria wide-host-range-phages and exhibit several distinct lineage-specific traits. Specifically, SL782 universally lacks a gene otherwise unique to and conserved in serotype 4b and harbors the Listeria pathogenicity island LIPI-4, while SL1039 harbors LIPI-3 and is almost always resistant to tetracycline, harboring the novel Tn916-like transposon Tn916.1039. These and other traits may have driven clonal emergence of SL782 and SL1039, potentially via adaptations in natural ecosystems.

microbiology↗

bioRxiv2025

American black bear (Ursus americanus) as a potential host for Campylobacter jejuni

The Gram-negative bacterium Campylobacter jejuni is part of the commensal gut microbiota of numerous animal species and a leading cause of bacterial foodborne illness in humans. Most complete genomes of C. jejuni are from strains isolated from human clinical, poultry, and ruminant samples. Here, we characterized and compared the genomes of C. jejuni that were isolated from American black bears in three states in the southeastern United States. Despite the limited sample size (n=9), the isolates displayed substantial genotypic variability, including eight distinct sequence types (STs) and variable gene content encoding surface glycan structures such as capsular polysaccharides (CPS) and lipooligosaccharides (LOS). Phylogenetic analysis identified several C. jejuni host generalist strains among the isolates from bears that clustered with isolates from domestic poultry, cattle, and environmental sources. Three isolates (SKBC94, SKBC3, SKBC5) clustered with wildlife-associated strains, exhibiting mutations or deletions in loci associated with cytolethal distending toxin production and oxidative stress resistance, potentially influencing host-specific colonization. Additionally, strains SKBC3 and SKBC5 harbored distinct Entner-Doudoroff (E-D) loci, suggesting a potential evolutionary fitness advantage. This study provides the first evidence of C. jejuni colonization in American black bears, highlighting their potential role as reservoirs for diverse C. jejuni lineages from both anthropogenic and environmental sources. Further research is needed to determine the prevalence and host specificity of C. jejuni strains in black bears and their potential implications for public and wildlife health.

microbiology↗

bioRxiv2023

Large-scale phenotypic and genomic characterization of Listeria monocytogenes susceptibility to quaternary ammonium compounds

Listeria monocytogenes is a significant concern for the food industry due to its ability to persist in the food processing environment. Decreased susceptibility to disinfectants is one of the factors that contribute to the persistence of L. monocytogenes. The objective of this study was to explore the diversity of L. monocytogenes susceptibility to quaternary ammonium compounds (QACs) using 1,671 L. monocytogenes isolates. This was used to determine the phenotype-genotype concordance and characterize genomes of the QAC sensitive and tolerant isolates for stress resistance, virulence and plasmid replicon genes. Distribution of QAC tolerance genes among 37,897 publicly available L. monocytogenes genomes were also examined. The minimum inhibitory concentration to QACs was determined by the broth microdilution method and non-sequenced isolates (n=1,244) were whole genome sequenced. Genotype-phenotype concordance was 99% for benzalkonium chloride, DDAC and a commercial QAC based sanitizer. Prevalence of QAC tolerance genes was 23% and 28% in our L. monocytogenes collection and in the global dataset, respectively. qacH was the most prevalent gene in our collection (61%), with 19% prevalence in the global dataset. Notably, bcrABC was most common (72%) globally, while 25% in our collection. Prevalence of emrC and emrE was comparable in both datasets, 7% and 2%, respectively. Replicon genes, indicative of plasmid harborage, were detected in 44% of the isolates and associated with the QAC tolerant phenotype. The presented analysis is based on the biggest L. monocytogenes collection in diversity and quantity for characterization of the L. monocytogenes QAC tolerance at both phenotypic and genomic levels. IMPORTANCEContamination of Listeria monocytogenes within the food processing environment is of concern to the food industry due to challenges in eradicating the pathogen once it becomes persistent in the environment. Genetic markers associated with increased tolerance to disinfectants have been identified, which alongside factors favor the persistence of L. monocytogenes in the production environment. By employing a comprehensive large-scale phenotypic testing and genomic analysis our study significantly enhances the understanding of the prevalence of quaternary ammonium compound (QAC) tolerant L. monocytogenes and the genetic determinants associated with the increased tolerance. Furthermore, we report on the prevalence of QAC tolerance genes among 37,897 publicly available L. monocytogenes sequences and their distribution within clonal complexes, isolation sources and geographical locations. As the propagation of QAC tolerance showed not be evenly distributed globally this highlights that understanding the development of L. monocytogenes disinfectant tolerance can be monitored using publicly available WGS data.

microbiology↗