Characterization of antimicrobial resistance and class 1 integrons in Enterobacteriaceae isolated from Mediterranean herring gulls (Larus cachinnans).

Mediterranean herring gulls (Larus cachinnans) were investigated as a possible reservoir of antibiotic resistant bacteria and of cassette-borne resistance genes located in class 1 integrons. Two hundred and fourteen isolates of the family Enterobacteriaceae were collected from cloacal swabs of 92 chicks captured in a natural reserve in the North East of Italy. They showed high percentages of resistance to ampicillin and streptomycin. High percentages of resistance to trimethoprim=sulfamethoxazole were found in Proteus and Citrobacter and to chloramphenicol in Proteus. Twenty-two (10%) isolates carried the intI1 gene. Molecular characterization of the integron variable regions showed a great diversity, with the presence of 11 different cassette arrays and of one integron without integrated cassettes. From this study it is concluded that the enteric flora of Mediterranean herring gulls may act as a reservoir of resistant bacteria and of resistance genes.