Antimicrobial resistance and phylogenetic groups in Escherichia coli isolates from Gulls of Berlengas natural reserve

Resumen

Fifty-three faecal samples from yellow-legged gulls (Larus cachìnnans) at the Berlengas nature reserve in Portugal were cultured on Levine agar plates not supplemented with antimicrobial agents, and one Escherichia coli colony was isolated and identified from each sample. The percentages of resistant isolates for each of the drugs were ampicillin (43.4 per cent), tetracycline (39.6 per cent), nalidixic acid (34.0 per cent), streptomycin (32.l per cent), trimethoprim-sulfamethoxazole (SXT) (26-4 per cent), ciprofloxacin (18-9 per cent), chloramphenicol (18.9 per cent), gentamicin (7.5 per cent), tobramycin (7.5 per cent) amikacin (5.7 per cent) and amoxicillin-clavulanic acid (1.9 per cent). All the isolates were susceptible to cefoxitin, ceftazidime, cefotaxime, aztreonam and imipenem. The following resistance genes were detected: h/αTEM (17 of 23 ampicillin-resistant isolates), tet(A) and/or tet(B) (18 of 21 tetracycline-resistant isolates), aadA (12 of 17 streptomycin-resistant isolates), cm/A (all chloramphenicol-resistant isolates), aac(3)-ll with or without ασc(3)-IV (all four gentamicin-resistant isolates), and sull and/or sul2 and/or sul3 (all 14 SXT-resistant isolates). The intll gene was detected in 10 of 14 SXT-resistant isolates, and three of them also contained class 2 integrons; four different gene cassette arrangements were identified among class I integrons (aadA, dfrAI+aadAI, dfrAI2+orfF+aadA2 and sat+psp+aadA2) and one among the class 2 integrons (dfrAI+sat+aadAI). Ninety per cent of the isolates were included in the A or BI phylogenetic groups.