Differences in co-selection and localization of antimicrobial resistance and virulence genes among Acinetobacter isolates from patients, pig waste, and the environment.

Abstract

Acinetobacter species are indigenous bacteria in water environments, whereas in clinical settings, they can pose a serious risk of nosocomial infection as opportunistic pathogens harboring multidrug-resistance genes. Understanding the similarities and differences in pathogenicity and drug resistance among Acinetobacter strains isolated from animals, humans, and the environment through a One Health approach is essential for mitigating their infection risk. We explored the resistome and virulome of 38 Acinetobacter isolates obtained from pigs' waste, patients, wastewater, and wastewater-impacted environments, including river and coastal area which receives wastewater effluent. Hybrid genome assemblies demonstrated distinct difference in the composition and location of antibiotic resistance genes (ARGs). Patient- and environment-associated isolates demonstrated chromosomally integrated ARGs and genes encoding efflux pumps, whereas pig waste-associated isolates exhibited a diverse range of ARG types predominantly located on plasmid replicons. Additionally, an analysis of virulence genes (VGs) across all Acinetobacter isolates revealed that VGs are more prevalent in patient- and environment-associated isolates compared to pig waste-associated isolates. Notably, a positive correlation between the number of ARGs and VGs located on the chromosome was observed in environment-associated isolates, which may imply co-selection of ARGs and VGs. Overall, this study highlights differences in the localization and co-selection of ARGs and VGs among patient-, pig waste-, and environment- associated isolates, suggesting that Acinetobacter spp. adapted to the human body tend to possess VGs and ARGs together, while those derived from animals may preferentially harbor transferable ARGs.