WIDESPREAD PRESENCE OF dfrA12 AND ITS ASSOCIATION WITH dfrA12-aadA2 CASSETTE IN SALMONELLA ENTERICA ISOLATES FROM SWINE

One hundred and eighty-nine Salmonella isolates from swine were tested for susceptibility to nine antimicrobial agents, presence of dfrA12 and class 1 inte- grons containing dfrA12-orfF-aadA2 cassette. All isolates were multidrug resistant and exhibited highest resistance prevalence to trimethoprim (93%). Most isolates (89%) were intl1-positive and 107 isolates (57%) carried dfrA12, all of which were resistant to trimethoprim. Forty-eight dfrA12-harboring strains (45%) were intl1- positive together with dfrA12-aadA2 gene cassette. Fifteen isolates contained dfrA12 but not intl1 and dfrA12-aadA2 cassette. The results indicated a wide distribution of dfrA12 and its role in dissemination of trimethoprim resistance among Salmonella isolates from fattening pigs.