Integrones y cassettes genéticos de resistencia a antimicrobianos en cepas de Shigella flexneri / Integrons and antimicrobial resistance gene cassettes in Shigella flexneri strains

ABSTRACT

BACKGROUND: The resistance of Shigella flexneri to antimicrobial agents can be associated to the presence of integrons that may contain and express antimicrobial resistance gene cassettes. AIM: To study antimicrobial resistance and the presence of integrons and antimicrobial gene cassettes in Shigella flexneri strains. MATERIAL AND METHODS: In vitro susceptibility to 27 antimicrobials was studied in twenty four Shigella flexneri strains isolated from stools. The presence of integrons class 1, 2 and 3 and antimicrobial resistance gene cassettes was investigated by polymerase chain reaction (PCR) using specific primers for each gene. RESULTS: Most strains were resistant to one of the following antimicrobials: ampicillin, sulphonamide, trimethoprim, tetracycline, streptomycin, sulfamethoxazole-trimethoprim or chloramphenicol. Twenty nine percent were simultaneously resistant to all these antimicrobials. Integrons class 1 and 2 were found in 19 strains (79 per cent). Class 3 integrons were not found. Gene cassettes dfrA1 and ant(3")I were associated to integrons class 2 in most strains (15/20, 75 per cent). Genes cat, tetB and blarTEM were detected in 18/24 (75 per cent), 7/24 (29 per cent) and 4/24 (17 per cent) of the strains, respectively and were not associated to any of the studied integrons. Genes that codify enzymes AAC(6')Ib and APH(3')VI were not detected in any strain. CONCLUSIONS: The high frequency of integrons found in the studied strains, could partly explain the increasing antimicrobial resistance of Shigella flexneri strains, isolated in Chile.