Diversity of species and antibiotic resistance among fecal enterococci from wild birds in Tunisia. Detection of vanA-containing Enterococcus faecium isolates

Abstract

Avifauna could be vectors of resistant bacteria including enterococci, but scarce information does exist about prevalence of antibiotic-resistant bacteria on bird populations, especially in the African Continent. Fecal samples of 111 birds (66 residents, 45 migratory) were taken in Tunisia in 2012. They were inoculated in Slanetz-Bartley agar supplemented or not with 8 μg/mL vancomycin (SB-Van and SB plates, respectively) for enterococci and vancomycin-resistant-enterococci (VRE) recovery. Enterococci were recovered in SB-plates in 73 of 111 samples (65.8 %) and one enterococci/positive sample was further studied: 60 Enterococcus faecium, 6 Enterococcus faecalis, 3 Enterococcus casseliflavus, 3 Enterococcus gallinarum, and 1 Enterococcus durans. Percentages of antimicrobial resistance identified were as follows: erythromycin (53.4 %), ciprofloxacin (41.1 %), tetracycline (19.2 %), pristanamycin (17.8 %), kanamycin, gentamicin or streptomycin (6.8–16.4 %), and ampicillin (0 %). Most of erythromycin-resistant and tetracycline-resistant enterococci carried the erm(B) and tet(M)+/−tet(L) genes, respectively. Most of high-level gentamicin or kanamycin resistant isolates carried the aac(6’)-Ie-aph(2”)-Ia or aph(3’)-IIIa genes, respectively, and 40 % of high-level streptomycin-resistant isolates the ant(6)-Ia gene. The vat(D) gene was detected in 46 % of pristinamycin-resistant enterococci and the cat(A) gene in 40 % of chloramphenicol-resistant enterococci. The gel(E), ace, or hyl genes were detected in 8–12 % of enterococci. VRE was detected in four of the birds, when SB-Van plates were used. These isolates were identified as E. faecium and carried the vanA gene, as well as the erm(B), tetM, aph (3’)-IIIa, and vatD genes, but not the hyl and esp virulence genes. Wild birds are occasional carriers of vanA-containing enterococci that could have implications in public health.