Objective   To analyze the drug resistance of Shigella integrons and their stability.    Methods   Drug-resistant gene cassettes of classes 1 and 2 Shigella integrons were cloned and transformed to E. coli DH5α

respectively

to observe changes in sensitivity of positive clones to multiple antibiotics. Positive clones were conjugated with multi-drug resistant Shigella integrons to conduct plasmid conjugating experiments

and drug resistance of and conjugants to antibiotics was detected. Ten drug-resistant S. flexneri strains with different resistant phenotypes and integrons were cultured continuously without any antibiotics

and changes in their resistance and integrons were detected.    Results   The minimal inhibitory concentration (MIC) of streptomycin and trimethoprim was increased 8-fold and 32-fold

respectively

for the positive clones of class 1 integron gene cassettes dfrA17-aadA5

and 64-fold and 32-fold

respectively

for the positive clones of class 2 integron gene cassettes dfrA1-sat1-aadA1. No change occurred in their drug resistance after conjugation. After 30 times of inoculation without antibiotics

one S. flexneri strain of class 2 Shigella integrons completely lost its resistance andintegron.    Conclusion   The integron gene cassettes in Shigella can lead to resistance to specific antibiotics and may have no impact on the resistance transferred by plasmid conjugate. Loss of class 2 integrons may occur in Shigella.