Similar antimicrobial resistance and virulence profiles among Aeromonas isolates from recreational beaches, post-chlorinated wastewater and clinical samples in Milwaukee, Wisconsin USA

Abstract

The genus Aeromonas consists of Gram-negative facultative anaerobes that are ubiquitous in water and soil environments. Traditionally considered fish pathogens, members of the genus Aeromonas have received increasing attention over the years due to their association with human diseases. Furthermore, given their omnipresence and genetic flexibility, this genus is positioned at the intersection of One Health components and may disproportionately contribute to the dissemination of antimicrobial resistance (AMR) in the environment. To form a more complete picture of the relationship between Aeromonas and AMR dissemination, we assessed the prevalence, species composition, AMR and virulence profiles, and cytotoxicity of Aeromonas isolates from post-chlorinated wastewater effluents (WW), adjacent beach sands, and local clinics. Our data show that Aeromonas represents approximately 22–50 % of culturable bacteria across all three beaches. The species composition across beaches, WW, and the clinic were similar, and two of the four most notable pathogens, A. hydrophila and A. caviae, were present in all three sources. Conversely, AMR and multi-drug resistant (MDR) populations were significantly more prevalent in WW and the clinic compared to the beaches. Assessments of virulence genes and cytotoxic phenotypes revealed that while isolates carrying act were significantly associated with cytotoxic phenotypes, there were minimal differences between cytotoxicity and source, despite the relative abundance of act and hlyA in the clinic compared to the beach and WW. Our data suggests that environmental Aeromonas populations may be capable of higher AMR acquisition rates potentially causing infection in humans to a greater extent than is currently observed.