Do wildlife omnivores and herbivores serve as a source of multidrug-resistant and pathogenic Escherichia coli strains in Poland? Analysis with reference to the host species range

Abstract

The phenomenon of resistance of Escherichia coli strains in free-living animals has been constantly expanding in recent years. However, the data is still fragmented and, due to the growing threat to public health, there is a constant need to search for and analyse new reservoirs and indicate their role and importance in the circulation of resistance genes. Therefore, the target group in this study were free-living non-predatory animals as reservoirs of drug-resistant and potentially virulent E. coli strains. For isolation, we used a combination of selective media with four antimicrobials. After additional two-stage analysis of strain similarity, we obtained 70 different isolates, including 71.4% of multidrug-resistant strains. In strains isolated from all species of animals, we determined high resistance to ampicillin (95.7%), tetracycline (64.3%), streptomycin (51.4%), and chloramphenicol (38.6%). Every third of the E. coli-positive individual was a carrier of more than one resistant clone. Moreover, four isolates among the resistant strains had the ExPEC pathotype, two had the ETEC pathotype, and another two represented EHEC.Our study confirmed that not only free-living predatory animals are reservoirs of resistance but also many synanthropic species of herbivores and omnivores contribute substantially to the spread of resistant and virulent E. coli strains.