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

The phenotypic resistance of 56 <i>Enterococcus faecalis</i> 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 various MGEs previously reported in human, food and livestock isolates, suggesting that vultures may acquire antibiotic-resistant bacteria (ARBs) and/or ARGs as a consequence of anthropogenic pollution. Overall, 22 virulence-associated genes encoding cell surface and secreted factors were identified, some of which were located on MGEs that also carried ARGs. The significant proportion of <i>E. faecalis</i> isolates recovered from vultures that exhibited MDR phenotypes and harbored MGEs carrying ARGs and virulence-associated genes is cause for concern, since vultures may act as spreaders of these genes to the environment, domestic animals and humans.