Aeromonas hydrophila and Aeromonas veronii Predominate among Potentially Pathogenic Ciprofloxacin- and Tetracycline-Resistant Aeromonas Isolates from Lake Erie

Members of the genusAeromonas are ubiquitous in nature and have increasingly been implicated in numerous diseases of humans and other animal taxa. Although some species of aeromonads are human pathogens, their presence, density, and relative abundance are rarely considered in assessing water quality. The objectives of this study were to identifyAeromonas species within Lake Erie, determine their antibiotic resistance patterns, and assess their potential pathogenicity.Aeromonas strains were isolated from Lake Erie water by use ofAeromonas selective agar with and without tetracycline and ciprofloxacin. All isolates were analyzed for hemolytic ability and cytotoxicity against human epithelial cells and were identified to the species level by using 16S rRNA gene restriction fragment length polymorphisms and phylogenetic analysis based ongyrB gene sequences. A molecular virulence profile was identified for each isolate, using multiplex PCR analysis of six virulence genes. We demonstrated thatAeromonas comprised 16% of all culturable bacteria from Lake Erie. Among 119Aeromonas isolates, six species were identified, though only two species (Aeromonas hydrophila andA. veronii ) predominated among tetracycline- and ciprofloxacin-resistant isolates. Additionally, both of these species demonstrated pathogenic phenotypesin vitro . Virulence gene profiles demonstrated a high prevalence of aerolysin and serine protease genes amongA. hydrophila andA. veronii isolates, a genetic profile which corresponded with pathogenic phenotypes. Together, our findings demonstrate increased antibiotic resistance among potentially pathogenic strains of aeromonads, illustrating an emerging potential health concern.