Characterization of vanA-containing Enterococcus faecium isolates carrying Tn5397-like and Tn916/Tn1545-like transposons in wild boars (Sus Scrofa).

The presence of vanA-containing Enterococcus faecium isolates was demonstrated in two of 67 fecal samples (3%) of healthy wild boars recovered in Portugal. One isolate per sample was studied further (E. faecium PG5V and PG48V). The mechanisms of resistance for other antibiotics were analyzed in these two vancomycin-resistant isolates, as well as the presence of genes related with virulence factors. The tet(M), tet(L), and erm(B) genes, associated with tetracycline or erythromycin resistance, were identified in both isolates, and the presence of aph(3')-IIIa gene (associated with kanamycin resistance) was detected in one of them. E. faecium PG48V exhibited an ampicillin minimum inhibitory concentration (MIC) of 64 microg/ml and showed eight amino acid substitutions in the carboxy-terminal end of the PBP5 protein (461Q --> K, 470H --> Q, 485M --> A, 496N --> K, 499A --> T, 525E --> D, 586V --> L, and 629E --> V) with respect to the reference sequence (GenBank accession number X84860). The purK-6 allele was identified in isolate PG48V, which also harbored the cylL(L)L(S), entA, and entB genes, encoding cytolysin, enterocin A, and enterocin B, respectively. The purK-3 allele was found in the PG5V isolate. The two vanA-containing isolates harbored the Tn916/Tn1545-like mobile element, and the Tn5397-like transposon was also found in isolate PG48V. The intestinal tract of wild boars could be a reservoir of vanA-containing enterococci.