Study on the mechanism of integron mediated multi-resistance in E. coli and Klebsiella

Objective To investigate the molecular mechanism of integron mediated multi-resistance in E. coli and Klebsiella. Methods Antibiotic susceptibility of 61 strains of clinical isolated E. coli and Klebsiella was tested by K-B method. ClassⅠ,ⅡandⅢintegrons were detected by integrase gene PCR. The variable region of integron were amplified by integron PCR, and the PCR products were sequenced. Results 73. 8% (45/61) of the strains were shown to be classⅠintegron positive, two strains of E. coli were shown to be classⅡintegron positive, and no classⅢintegron was detected. 88. 9% (40/ 45) of the positive strains of classⅠintegron contained a gene cassette, which sized from 150 bp to 2 800 bp, and one classⅡintegron positive strain contained a 2200 bp size gene cassette. DNA sequencing was used to identify the genetic content of the integron variable regions. These gene cassettes included genes encoding resistance to aminoglycosides (aadA1, aadA2, aadA5, aadB, aacA4, aac6'-Ib ), sulfamethoxazole/trimethoprim (dfrA1, dfr 2d, dfrⅤ, dfrⅫ, dfr17), chloramphenicol (cat, catB8, cmlAl-variant) ,β-lactams (blaoxa10) and streptothricin (sat1). Conclusion Integrons are widespread in E. coli and Klebsiella and mediate the multi-resistance of the two species.