Antimicrobial resistance and virulence potential of non-faecium and non-faecalis enterococci isolated from canine rectal swabs.

Animals can serve as reservoirs for multidrug-resistant (MDR) enterococci with potential pathogenicity. Close contact between dogs and their owners may facilitate the interspecies transmission of these bacterial agents, potentially impacting human health. While Enterococcus faecium and Enterococcus faecalis are the main species implicated in healthcare-associated infections (HAIs), non-faecium and non-faecalis (NFF) enterococci, though less prevalent, may also contribute to infections. This study aimed to assess the antimicrobial resistance phenotypes and genotypes and virulence potential of NFF enterococci isolated from asymptomatic dogs. A total of 114 NFF enterococcal isolates were obtained from rectal swabs of dogs, between 2015 and 2017, in Rio de Janeiro, Brazil. Antimicrobial resistance was assessed using disk diffusion and agar gradient diffusion methods, and resistance and virulence genes were determined by polymerase chain reaction (PCR). The highest resistance frequencies were observed for rifampicin (38.6%), tetracycline (27.2%), and erythromycin (15.8%). One vancomycin-resistant E. gallinarum strain (MIC > 512 µg/mL) was isolated, and it also exhibited resistance to teicoplanin. High-level resistance to streptomycin (HLR-S) was found in E. canintestini (22.2%), E. gallinarum (8.5%), and E. avium (7.1%) strains. Most E. raffinosus strains were resistant to ampicillin (55%) and penicillin G (55%), and this was the only species resistant to ampicillin. MDR strains accounted for 14.9% of the strains, with MDR colonization more frequent in purebred dogs, suggesting a possible breed-related association. The resistance genes detected included ant(6)-Ia, tet(M), tet(L), erm(B), and the van operon. Virulence genes were detected in a limited number of strains: esp (11.4%), gelE (2.6%), asa1 (0.9%), and hyl (0.9%). The presence of esp was significantly associated with E. canintestini (44.4%), and E. avium (42.9%). Further studies are needed to evaluate the public health implications of these findings.