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 lt 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.

Crevna mikroflora životinja koje se koriste u ishrani ljudi, uključujući i crevnu mikrofloru živine, predstavlja potencijalni rezervoar gena rezistencije na antibiotike za bakterije koje su humani patogeni. U toku ove studije je iz različitih uzoraka uzetih od 29 zdravih i 18 bolesnih brojlera izolovano ukupno 47 sojeva Enterobacteriaceae od kojih je čak 43 identifikovano kao Escherichia coli. Kod svih izolata ispitana je osetljivost na 18 antibiotika, prisustvo integrona, kao i moguća povezanost integrona i rezistencije na antibiotike. Preko 80% izolata (82,9%) je bilo multirezistentno. Integroni su bili prisutni kod 68,1% izolata i to: integroni klase 1 kod 42,5%, integroni klase 2 kod 10,6%, a obe klase kod 14,9% sojeva. Treba istaći da je kod dva izolata sa klasom 1 integrona ustanovljeno prisustvo kasete aacA4-catB3-dfrA1, koja je do sada opisivana samo kod vrste Pseudomonas aeruginosa. Statistička analiza pokazala je značajnu povezanost prisustva integrona i multirezistencije (p lt 0,05). Gen merA, odgovoran za rezistenciju na živu, detektovan je kod 44,4% izolata sa klasom 1 integrona, što ukazuje na ulogu Tn21 transpozona u diseminaciji integrona unutar ispitivane grupe izolata. Ova studija pružila je prvi uvid u problem rezistencije i genetičku osnovu rezistencije izolata enetrobakterija kod živine u Grčkoj. Dobijeni rezultati ukazuju na potrebu uvođenja programa kontinuiranog praćenja rezistencije ovih bakterija, s obzirom na postojanje mogućnosti za transfer njihovih gena rezistencije na humane patogene.