Antibiotic Resistance to Critically Important Antimicrobials and Virulence Genes in Enterococcus Faecalis Strains Isolated from Eurasian Griffon (Gyps fulvus) Vultures and Their Association with Mobile Genetic Elements

The phenotypic resistance of 56 E. faecalis isolates from Eurasian griffon vultures was subjected to surveillance testing with the microdilution method using a standardized panel of antimicrobials. Isolates were also characterized by MLST. Additionally, the genome of 19 isolates with phenotypic resistance to linezolid, ciprofloxacin, chloramphenicol and/or high-level resistance to gentamicin were sequenced to determine their antimicrobial resistance (ARGs) and virulence-associated genes and to identify mobile genetic elements (MGEs). Most isolates (82.1%) exhibited non-wild-type phenotypes to six antimicrobial agents, and multidrug resistance (MDR) was detected in 34% of the isolates. Most MDR isolates (53%) belonged to ST16, ST116 and ST35. ARGs were localized on the chromosome as well as on different MGEs previously reported in humans, foods and livestock isolates, suggesting the exchange of antimicrobial-resistant bacteria and/or ARGs to vultures consequence of an anthropogenic pollution. Twenty-two virulence-associated genes encoding cell surface and secreted factors were identified, some of them located on MGEs that also carried ARGs. The significant proportion of E. faecalis isolates recovered from vultures exhibiting MDR phenotypes and harbored MGEs carrying ARGs and virulence-associated genes, is a cause for concern, since vultures may act as spreaders of these genes to the environment, domestic animals and humans.