Wild birds as biological indicators of environmental pollution: antimicrobial resistance patterns of Escherichia coli and enterococci isolated from common buzzards (Buteo buteo).

A total of 36 Escherichia coli and 31 enterococci isolates were recovered from 42 common buzzard faecal samples. The E. coli isolates showed high levels of resistance to streptomycin and tetracycline. The following resistance genes were detected: bla(TEM) (20 of 22 ampicillin-resistant isolates), tet(A) and/or tet(B) (16 of 27 tetracycline-resistant isolates), aadA1 (eight of 27 streptomycin-resistant isolates), cmlA (three of 15 chloramphenicol-resistant isolates), aac(3)-II with/without aac(3)-IV (all seven gentamicin-resistant isolates) and sul1 and/or sul2 and/or sul3 [all eight sulfamethoxazole/trimethoprim-resistant (SXT) isolates]. intI1 and intI2 genes were detected in four SXT-resistant isolates. The virulence-associated genes fimA (type 1 fimbriae), papC (P fimbriae) and aer (aerobactin) were detected in 61.1, 13.8 and 11.1% of the isolates, respectively. The isolates belonged to phylogroups A (47.2%), B1 (8.3%), B2 (13.9%) and D (30.5%). For the enterococci isolates, Enterococcus faecium was the most prevalent species (48.4%). High levels of tetracycline and erythromycin resistance were found among our isolates (87 and 81%, respectively). Most of the tetracycline-resistant strains carried the tet(M) and/or tet(L) genes. The erm(B) gene was detected in 80% of erythromycin-resistant isolates. The vat(D) and/or vat(E) genes were found in nine of the 17 quinupristin-dalfopristin-resistant isolates. The enterococcal isolates showing high-level resistance for kanamycin, gentamicin and streptomycin contained the aph(3')-IIIa, aac(6')-aph(2″) and ant(6)-Ia genes, respectively. This report reveals that common buzzards seem to represent an important reservoir, or at least a source, of multi-resistant E. coli and enterococci isolates, and consequently may represent a considerable hazard to human and animal health by transmission of these isolates to waterways and other environmental sources via their faecal deposits.