Biology subjects

Bosilevac, J. M.

Publications and source records attributed to Bosilevac, J. M..

3 recordsLinked to original sources

bioRxiv2026

Pathogenome and Plasmid-Borne Antimicrobial Resistance Phenotypes in a Multidrug-Resistant O111:H8 Shiga Toxin-Producing Escherichia coli Strain

Plasmids contribute to virulence and antimicrobial resistance in Shiga toxin-producing Escherichia coli (STEC). Here, the mobility, gene content, and evolutionary context of four plasmids carried by an O111:H8 STEC strain designated UTAK-22: pUTAK-22.1-MDR, pUTAK-22.2-MDR, pUTAK-22.3-P1, and pUTAK-22.4-pO111 were characterized. Conjugation experiments, phenotype-based selective readouts, and comparative genomics together showed that pUTAK-22.1-MDR is self-transmissible, whereas pUTAK-22.2-MDR and pUTAK-22.4-pO111 are most consistent with mobilization in trans, making use of the strain's native helper plasmid background, while pUTAK-22.3-P1 represents a conjugation-deficient IncY phage-derived replicon. Genome annotation and comparative analyses further highlighted the structural diversity and mosaic composition of these plasmids, including P1-like phage remnants, virulence loci, and distinct antimicrobial resistance modules. Phenotypic profiling of the native wild-type plasmid complement and selected transconjugants in the recipient E. coli strain WG5 further showed that the presence of co-resident plasmids and redundant resistance determinants results in dosage-dependent streptomycin tolerance. Together, these findings expand our understanding of the mobility landscape, evolutionary dynamics, and resistance potential of STEC plasmids, while underscoring the importance of interpreting resistance phenotypes in the context of a strain's natural plasmid composition.

microbiology↗

bioRxiv2025

Phylogenomic framework and virulence gene boundaries of emerging Shiga toxin producing Escherichia coli O118 informed by the comprehensive profiling of 359 O118 genomes

Non-O157 Shiga toxin-producing Escherichia coli (STEC), particularly the O118 serogroup, are emerging pathogens linked to severe foodborne illnesses, including hemolytic uremic syndrome. The hallmark of STEC virulence is the production of a potent phage-borne cytotoxin, often accompanied by the locus of enterocyte effacement (LEE). This study explores the genomic landscape, virulence factors, and resistance traits of O118 STEC. We analyzed 357 publicly available O118 genomes across ten H-antigens and included two clinically significant O118:H16 STEC strains sequenced to closure. Pangenome assessment and core genome multilocus sequence typing (MLST) based on 4,160 shared genes revealed phylogenetic clustering by H-type and delineated distinct STEC-phylogroups, alongside relationships to non-STEC pathovars such as uropathogenic E. coli (UPEC), enteropathogenic E. coli (EPEC), and enterotoxigenic E. coli (ETEC). Identified STEC phylogroups encompassed H6, H12, H16, and H2 strains with diverse Shiga toxin (stx) profiles (stx1a, stx2a, stx2b, stx2c, stx2f). A subset of H2-STEC lacked stx, suggesting potential secondary phage loss. Most STEC groups harbored the locus of enterocyte effacement (LEE). Further, a strong correlation was observed between H-antigens and eae subtypes, with specific pairings such as H6/eae-{iota}, H16/eae-{beta}, and H2/eae-{varepsilon}. Horizontally acquired pathogenicity islands--including O-island 122 in H16 strains and a novel pathogenicity-associated island carrying antibiotic resistance--along with other loci related to colonization and interbacterial competition, further enhance these strains virulence potential. Our findings underscore the genetic diversity and virulence potential of O118 STEC. Understanding phylogroup-specific traits and resistance markers is crucial for effective surveillance and public health interventions. ImportanceShiga toxin-producing Escherichia coli (STEC) are a major public health concern, responsible for illnesses ranging from diarrhea to life-threatening kidney damage. Among non-O157 STEC, serogroup O118 is increasingly recognized as an emerging STEC lineage. This study provides the most comprehensive genomic analysis to date of O118 STEC, offering critical insights into their pathogenome, virulence traits, and antimicrobial resistance inventories. Notably, we identified a novel 74 kb pathogenicity island in clinical strain H16-12089 that encodes a combination of multidrug resistance genes, virulence factors, and interbacterial competition systems. Understanding the genetic makeup and virulence potential of these pathogens is essential for improving surveillance, risk assessment, and public health interventions.

genomics↗

bioRxiv2020

Seasonal prevalence and characterization of Shiga toxin-producing Escherichia coli on pork carcasses at three steps of the harvest process at two commercial processing plants in the US

Shiga toxin (stx) -producing Escherichia coli (STEC) are foodborne pathogens that have a significant impact on public health, with those possessing the attachment factor intimin (eae) referred to as enterohemorrhagic E. coli (EHEC) associated with life threatening illnesses. Cattle and beef are considered typical sources of STEC, but their presence in pork products is a growing concern. Therefore, carcasses (n=1536) at two U.S. pork processors were sampled once per season at three stages of harvest (post-stunning skins; post-scald carcasses; chilled carcasses) then examined using PCR for stx and eae, aerobic plate count (APC) and Enterobacteriaceae counts (EBC). Skins, post-scald, and chilled carcasses had prevalence of stx (85.3, 17.5, and 5.4%, respectively), with 82.3, 7.8, and 1.7% respectively, having stx and eae present. All stx positive samples were subjected to culture isolation that resulted in 368 STEC and 46 EHEC isolates. The most frequently identified STEC were serogroup O121, O8, and O91(63, 6.7, and 6.0% of total STEC, respectively). The most frequently isolated EHEC was serotype O157:H7 (63% of total EHEC). Results showed that scalding significantly reduced (P < 0.05) carcass APC and EBC by 3.00 and 2.50 log10 CFU/100 cm2 respectively. A seasonal effect was observed with STEC prevalence lower (P < 0.05) in winter. The data from this study shows significant (P < 0.05) reduction in the incidence of STEC (stx) from 85.3% to 5.4% and of EHEC (stx+eae) from 82.3% to 1.7% within slaughter-to-chilling continuum, respectively, and that potential EHEC can be confirmed present throughout using culture isolation. IMPORTANCESeven serogroups of Shiga toxin-producing Escherichia coli (STEC) are responsible for most (>75%) cases of severe illnesses caused by STEC and are considered adulterants of beef. However, some STEC outbreaks have been attributed to pork products although the same E. coli are not considered adulterants in pork because little is known of their prevalence along the pork chain. The significance of the work presented here is that it identifies disease causing STEC, enterohemorrhagic E. coli (EHEC), demonstrating that these same organisms are a food safety hazard in pork as well as beef. The results show that most STEC isolated from pork are not likely to cause severe disease in humans and that processes used in pork harvest, such as scalding, offer a significant control point to reduce contamination. The results will assist the pork processing industry and regulatory agencies to optimize interventions to improve the safety of pork products.

microbiology↗