Prevalence of Enterococcus spp. and the Whole-Genome Characteristics of Enterococcus faecium and Enterococcus faecalis Strains Isolated from Free-Living Birds in Poland

Abstract

Enterococci as opportunistic bacteria are important for human health. Due to the prevalence and ease of acquisition and transfer of their genes, they are an excellent indicator of environmental contamination and the spread of antimicrobial resistance. The aim of the study was to assess the prevalence of Enterococcus spp. in wild birds in Poland, determination of antimicrobial susceptibil-ity and WGS analysis of Enterococcus (E.) faecium and E. faecalis. For this purpose, 138 samples from various species of free-living birds were tested, with 66.7% positive results. 14 species were detected, with E. faecalis being the most common, followed by E. casseliflavus and E. hirae. In anti-microbial susceptibility testing, 16.0% of E. faecalis and 50.0% of E. faecium showed resistance to one antimicrobial agent, in addition the MDR phenotype was found in one E. faecium. The most common resistance phenotype included tetracycline and quinupristin/dalfopristin. The WGS anal-ysis confirmed the significant advantage of the virulence gene diversity of E. faecalis strains over E. faecium. In addition, plasmid replicons were found in 42.0% of E. faecalis and 80.0% of E. faecium. The obtained results confirm free-living birds can be a reservoir of Enterococcus spp. with a consid-erable zoonotic potential.