Detection of vancomycin-resistant Enterococcus faecalis ST6-vanB2 and E. faecium ST915-vanA in faecal samples of wild Rattus rattus in Spain

The detection of vancomycin-resistant-enterococci (VRE) among wild animals represents a worrisome public health concern. The objectives of the study were to determine the possible presence of VRE in faecal samples of wild small mammals in Spain, to characterize the vancomycin resistance mechanisms and genetic lineages of recovered isolates and to know the diversity of enterococcal species in these animals. A total of 155 faecal samples from small mammals were inoculated in Slanetz-Bartley agar supplemented or not with vancomycin (Van-SB/SB plates). The antimicrobial susceptibility profile to 12 antimicrobials and the presence of 20 antimicrobial resistance genes was analyzed. The structure of Tn1546 and the presence of gelE, cylA, asa, esp and hyl genes was studied. Multilocus-sequence-typing (MLST) technique was also performed. VRE isolates were recovered in Van-SB plates in 11 samples. Two samples contained vanB2-positive E. faecalis isolates of lineage ST6, which showed a multiresistance phenotype and harboured the virulence genes gelE and asa. One sample contained a vancomycin-resistant E. faecium isolate of the new lineage ST915, with the vanA gene included into Tn1546 (truncated with IS1542 and IS1216 elements). The vanB2 and vanA isolates were obtained from Rattus rattus. The remaining eight VRE-positive samples contained species with intrinsic vancomycin-resistance mechanisms: E. casseliflavus (n=5) and E. gallinarum (n=3). One hundred and forty-seven vancomycin-susceptible-enterococcal isolates were obtained in SB plates, and E. faecalis and E. faecium were the most frequent detected species. This is the first report of vanB2-containing enterococci in wild animals.