Transfer patterns of integron-associated and antibiotic resistance genes in S. flexneri during different time intervals in Tianjin, China

Conclusion: Of the 32 strains of S. flexneri isolated from 1981 to 1983 and stored in our laboratory, class 1 integron was detected in 28 strains (87.50%), while 27 strains (84.37%) harboured an aminoglycoside resistance gene, aadA, in the variable region of their integrons. Class 1 integron was identified in 22 (91.67%) of the 24 S. flexneri strains isolated from 2009 to 2010, whereas the variable region and 3′-end amplification were not present in any of the strains. Class 2 integron was not found in the 1981-1983 group (group A) of strains; although 19 (79.17%) of the 24 strains in the 2009-2010 group (group B) possessed class 2 integron, and the variable region of the integron harboured dfrA1 + sat1 + aadA1 genes, which, respectively, mediate antibiotic resistance to trimethoprim, streptothricin and streptomycin. Seventeen strains of the total 56 possessed both class 1 and 2 integrons. Strains belonging to group A were highly resistant to tetracycline, chloramphenicol and a combination of trimethoprim-sulfamethoxazole; 65.63% of the strains were multi-resistant to three or more antibiotics. In group B, the strains showed high resistance to ampicillin, trimethoprim-sulfamethoxazole, piperacillin and tetracycline; 83.33% of the strains were multi-resistant to three or more antibiotics. Class 1 and 2 integrons exist extensively in S. flexneri, and the 3′-conserved segments of class 1 integron m...
Source: Indian Journal of Medical Microbiology - Category: Microbiology Authors: Source Type: research