Distribution and content of class 1 integrons in different Vibrio cholerae O-serotype strains isolated in Thailand.
In this study, 176 clinical and environmental Vibrio cholerae strains of different O serotypes isolated in Thailand from 1982 to 1995 were selected and studied for the presence of class 1 integrons, a new group of genetic elements which carry antibiotic resistance genes. Using PCR and DNA sequencing, we found that 44 isolates contained class 1 integrons harboring the aadB, aadA2, blaP1, dfrA1, and dfrA15 gene cassettes, which encode resistance to gentamicin, kanamycin, and tobramycin; streptomycin and spectinomycin; beta-lactams; and trimethoprim, respectively. Each cassette array contained only a single antibiotic resistance gene. Although resistance genes in class 1 integrons were found in strains from the same epidemic, as well as in unrelated non-O1, non-O139 strains isolated from children with diarrhea, they were found to encode only some of the antibiotic resistance expressed by the strains. Serotype O139 strains did not contain class 1 integrons. However, the appearance and disappearance of the O139 serotype in the coastal city Samutsakorn in 1992 and 1993 were associated with the emergence of a distinct V. cholerae O1 strain which contained the aadA2 resistance gene cassette. A 150-kb self-transmissible plasmid found in three O1 strains isolated in 1982 contained the aadB gene cassette. Surprisingly, several strains harbored two integrons containing different cassettes. Thus, class 1 integrons containing various resistance gene cassettes are distributed among different V. cholerae O serotypes of mainly clinical origin in Thailand.
Dalsgaard
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A
Department of Veterinary Microbiology, Royal Veterinary and Agricultural University, Frederiksberg, DK-1870 Frederiksberg C. ad@kvl.dk
Forslund
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A
Serichantalergs
O
O
Sandvang
D
D
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D033364:Decapoda / Q000382:microbiology; D004352:Drug Resistance, Microbial / Q000235:genetics*; D004783:Environmental Microbiology; D005506:Food Contamination; D005516:Food Microbiology; D005798:Genes, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D017747:Seafood / Q000382:microbiology; D013785:Thailand; D014734:Vibrio cholerae / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents