High frequency of B2 phylogroup among non-clonally related fecal Escherichia coli isolates from wild boars, including the lineage ST131

Abstract

Wild boars are worldwide distributed mammals which population is increasing in many regions, like the Iberian Peninsula, leading to an increased exposition to humans. They are considered reservoirs of different zoonotic pathogens and have been postulated as potential vectors of antimicrobial-resistant (AMR) bacteria. This study aimed to determine the prevalence of antimicrobial resistance and phylogenetic distribution of Escherichia coli from wild boar feces. Antimicrobial resistance and integron content was genetically characterized and E. coli of B2 phylogroup was further analyzed by molecular typing and virulence genotyping. The prevalence of AMR E. coli was low, with only 7.5% of isolates being resistant against at least one antimicrobial, mainly ampicillin, tetracycline and/or sulfonamide. An unexpected elevated rate of B2 phylogroup (47.5%) was identified, most of them showing unrelated pulsed-field-gel-electrophoresis patterns. ST131/B2 (fimH 22 sublineage), ST28/B2, ST1170/B2, ST681/B2 and ST625/B2 clones, previously described in extraintestinal infections in humans, were detected in B2 isolates, and carried one or more genes associated with extraintestinal pathogenic E. coli (ExPEC). This study demonstrated a low prevalence of antimicrobial resistance in E. coli from wild boars, although they are not exempt of AMR bacteria, and a predominance of genetically diverse B2 phylogroup, including isolates carrying ExPEC which may contribute to the spread of virulence determinants among different ecosystems.

Keywords: B2 phylogroup; Escherichia coli; ST131; antimicrobial resistance; virulence genes; wild boars.