Molecular characterization of the integrons in Shigella strains isolated from patients with traveler's diarrhea

The prevalence and characterization of Class 1 integrons has been performed in eighty three strains of Shigella spp., isolated between 1995 and 2000 from patients with traveler's diarrhea. A low prevalence (13.25%) was recorded. Nine different integrons were found among 11 multiresistant strains, with a total of 10 different gene cassettes encoding for resistance to trimethoprim (dfrA1, dfrA5, dfrA7, dfrA12, and dfrA15), aminoglycosides (aadA1a and aadA2), β-lactam antibiotics (oxa2) or ORF with unknown function (orfD and orfF). A high prevalence of dfr and aad gene cassettes was observed. The low incidence of Class 1 integrons observed in this study is in contrast with the known facility that the Shigella genus has to gain and transfer plasmids.