Strains Isolated from American Bison () Showed Uncommon Virulent Gene Patterns and Antimicrobial Multi-Resistance.

is considered one of the most important zoonotic pathogens worldwide. Highly virulent and antimicrobial-resistant strains of have been reported in recent years, making it essential to understand their ecological origins. In this study, we analyzed the characteristics of strains present in the natural population of American bison () in Mexico. We sampled 123 individuals and determined the presence of using standard bacteriological methods. The isolated strains were characterized using molecular techniques based on PCR. To evaluate the diversity of strains in this population, we analyzed 108 suggestive colonies from each fecal sample. From a total of 13,284 suggestive colonies, we isolated 33 strains that contained at least one virulence gene. The virotypes of these strains were highly varied, including strains with atypical patterns or combinations compared to classical pathotypes, such as the presence of V, , B, and genes in strain LMA-26-6-6, or 2, , and genes in strain LMA-16-1-32. Genotype analysis of these strains revealed a previously undescribed phylogenetic group. Serotyping of all strains showed that serogroups O26 and O22 were the most abundant. Interestingly, strains belonging to these groups exhibited different patterns of virulence genes. Finally, the isolated strains demonstrated broad resistance to antimicrobials, including various beta-lactam antibiotics.