ABSTRACT
Objective To analyze the distribution of class 1,2 and 3 integrons and their gene cassettes,and to explore its relationship with drug resistance in Shigella.Methods Antimicrobial susceptibility was detected by minimal inhibitory concentration (MIC) method.All the genes of integrons and gene cassettes were amplified by polymerase chain reaction (PCR).The amplicons were identified by amplified fragment length polymorphism (AFLP) and sequencing.Results Fifty seven multi-drug resistant strains were identified from a total of 62 Shigella strains (91.9％).Among multi drug resistant strains,52 strains carried integrons of class 1 (91.2 ％) and 55 strains carried integrons of class 2 (96.5％).Only 2 strains carried class 1 integrons alone,5 strains carried class 2 integrons alone and 50 strains had both class 1 and class 2 integrons.Class 3 integrons were not detected.The gene cassettes of typical class 1 integrons,dfrV and dfrA17-aadA5,were detected in 6 strains and 2 strains,respectively.Atypical class 1 integrons with gene cassettes blaOxA30 aadA1 were detected in 44 strains.The typical and atypical class 1 integrons coexisted in 6 Shigella flexneri strains.Gene cassettes for class 2 integrons were dfrA1 sat1-aadA1.Conclusions The multi-drug resistant Shigella strains are widely distributed in Ji'nan,and the atypical class 1 integrons and class 2 integrons are common in these strains.Coexistence of the two integrons is observed in some of the strains.
