Multidrug resistance and integrons in Escherichia coli isolated from chicken in Greece

Abstract

Enteric faecal flora of food-producing animals such as poultry is a potential reservoir for antimicrobial resistance genes which can be transferred to human pathogens via the food chain. The present study investigated 47 strains of Enterobacteriaceae recovered from a variety of chicken specimens for their resistance to 18 antimicrobial agents and the presence of integrons, and analyzed the association between integrons and antimicrobial susceptibility. Multidrug resistance was found in 82.9% of the isolates. The presence of integrons was shown in 68.1% of the strains tested: 42.5% carried a class 1 integron, 10.6% carried a class 2 integron, and 14.9% had both class 1 and 2 integrons. An unusual cassette aacA4-catB3-dfrA1 was revealed in two class 1 integron-positive isolates. The association between the presence of an integron and multidrug resistance was significant (p<0.05). The mercury resistance gene, merA, was found in 44.4% of strains with class 1 integron, indicating the role of Tn21 transposon in dissemination of integrons within the samples studied. The study gives baseline information on the resistance problem and its genetic background in contemporary poultry Enterobacteriaceae in Greece, and suggest the need for the introduction of surveillance programs to monitor antimicrobial resistance that can be potentially transmitted to humans.