Molecular characterization of vancomycin-resistant enterococci and extended-spectrum β-lactamase-containing Escherichia coli isolates in wild birds from the Azores Archipelago

Abstract

To study the prevalence of vancomycin-resistant enterococci (VRE) and extended-spectrum β-lactamase (ESBL)-containing Escherichia coli isolates, and the mechanisms of resistance implicated, 220 faecal samples from wild birds were collected between 2006 and 2010 in the Azores Archipelago. Samples were spread on Slanetz–Bartley agar plates supplemented with 4 mg/l vancomycin and on Levine agar plates supplemented with 2 mg/l cefotaxime for VRE and ESBL-containing E. coli isolation, respectively. vanA-containing enterococcal isolates (four Enterococcus faecium and two Enterococcus durans) and vanC-1 Enterococcus gallinarum isolates were detected in six and seven faecal samples, respectively. VRE isolates showed ampicillin (n=11), ciprofloxacin (n=9), tetracycline (n=6), erythromycin (n=5), quinupristin/dalfopristin (n=3) and high-level kanamycin resistance (n=1). The tet(L) and/or tet(M) gene was found in all tetracycline-resistant isolates and the erm(B) gene in all erythromycin-resistant isolates. Three vanA-containing E. faecium and two E. gallinarum presented specific sequences of the Tn5397 transposon. Four VRE isolates harboured the ace virulence gene. One faecal sample revealed one ESBL-containing E. coli isolate that belongs to the A phylogenetic group, showed a phenotype of resistance to β-lactams and tetracycline, and harboured the bla CTX-M-14, bla SHV-12 and the tet(A) genes. To our knowledge, this is the first study to focus on defining the prevalence of VRE and/or ESBL-containing E. coli strains in wild birds from the Azores. The data recovered are essential to improve knowledge about the dissemination of resistant strains through wild ecosystems and their possible implications by transferring these resistances to other animals or to humans.