title: Antibiotic resistance conferred by a class I integron and SXT constin in Vibrio cholerae O1 strains isolated in Laos.
abstract: Changes in the drug susceptibility pattern were observed in Vibrio cholerae O1 isolated in the Lao People's Democratic Republic during 1993 to 2000. In this study, 50 V. cholerae O1 strains were selected during this period for studying the presence of class I integron and SXT constin. Twenty-four streptomycin-resistant strains out of 26 isolated before 1997 contained a class I integron harboring the aadA1 gene cassette. Twenty-four strains isolated after 1997 contained an SXT constin (a large conjugative element). Twenty of the strains were resistant to chloramphenicol, tetracycline, streptomycin, and trimethoprim-sulfamethoxazole, while four strains were susceptible to the antibiotic tested. The resistance genes included in the SXT constins were floR, tetA, strAB, and sulII, which encode resistance to chloramphenicol, tetracycline, streptomycin, and sulfamethoxazole, respectively. The antibiotic resistance gene cluster was found to be deleted in the four susceptible strains. SXT(LAOS) did not contain dfrA1 or dfr18, which confer resistance to trimethoprim in SXT(ET) and SXT(MO10), respectively. A hot spot region of SXT(LAOS) was sequenced, and we identified two novel open reading frames showing homology to sO24 (exonuclease) and sO23 (helicase) of the genomic island associated with the multidrug resistance region of Salmonella enterica serovar Typhimurium DT104. Analysis of SXT(LAOS) showed that there is a continuous flux of genes among V. cholerae SXT constins which should be carefully monitored.
authors.affiliation: Division of Bacterial Pathogenesis, Department of Microbiology, Graduate School of Medicine, University of the Ryukyus, Nishihara, Okinawa 903-0215, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Iwanaga
authors.forename: Claudia
authors.initials: C
authors.lastname: Toma
authors.forename: Tomoko
authors.initials: T
authors.lastname: Miyazato
authors.forename: Sithat
authors.initials: S
authors.lastname: Insisiengmay
authors.forename: Noboru
authors.initials: N
authors.lastname: Nakasone
authors.forename: Masahiko
authors.initials: M
authors.lastname: Ehara
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D003001:Cloning, Molecular; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D032023:Integrons / Q000235:genetics*; D007812:Laos; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D041241:Vibrio cholerae O1 / Q000187:drug effects / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C444447:o1 SXT constin protein, Vibrio cholerae