Different antibiotic resistance mechanisms associated with integrons in clinical isolates of Salmonella typhimurium

Antibiotic resistance in clinical isolates of Salmonella typhimurium has steadily risen in recent years. Some of the resistance genes may be carried into integrons. In this study, integrons, both from 10 epidemiologically related and unrelated S. typhimurium clinical isolates, were characterized, showing that epidemiologically different strains can carry the same integron, and that epidemiologically related strain can carry different integrons. Among the resistance genes detected in this study were genes encoding β-lactamases (bla_oxa-30 in two strains, and bla_pse-1 in five strains, one of which was carrying this cassette in two different integrons); aminoglycoside-modifyng enzymes (aadA2 in four strains, one of which was carrying this cassette in two different integrons, and aadA1 in six strains); as well dihydrofolate reductases (dfrAI in three strains).