Antimicrobial resistance, class 1 integrons, and genomic island 1 in Salmonella isolates from Vietnam

A.T. Vo, E. van Duijkeren, W. Gaastra, A.C. Fluit

    Research output: Contribution to journalArticleAcademicpeer-review


    Background: The objective was to investigate the phenotypic and genotypic resistance and the horizontal transfer of
    resistance determinants from Salmonella isolates from humans and animals in Vietnam.
    Methodology/Principal Findings: The susceptibility of 297 epidemiologically unrelated non-typhoid Salmonella isolates
    was investigated by disk diffusion assay. The isolates were screened for the presence of class 1 integrons and Salmonella
    genomic island 1 by PCR. The potential for the transfer of resistance determinants was investigated by conjugation
    experiments. Resistance to gentamicin, kanamycin, chloramphenicol, streptomycin, trimethoprim, ampicillin, nalidixic acid,
    sulphonamides, and tetracycline was found in 13 to 50% of the isolates. Nine distinct integron types were detected in 28%
    of the isolates belonging to 11 Salmonella serovars including S. Tallahassee. Gene cassettes identified were aadA1, aadA2,
    aadA5, blaPSE-1, blaOXA-30, dfrA1, dfrA12, dfrA17, and sat, as well as open reading frames with unknown functions. Most
    integrons were located on conjugative plasmids, which can transfer their antimicrobial resistance determinants to
    Escherichia coli or Salmonella Enteritidis, or with Salmonella Genomic Island 1 or its variants. The resistance gene cluster in
    serovar Emek identified by PCR mapping and nucleotide sequencing contained SGI1-J3 which is integrated in SGI1 at
    another position than the majority of SGI1. This is the second report on the insertion of SGI1 at this position. High-level
    resistance to fluoroquinolones was found in 3 multiresistant S. Typhimurium isolates and was associated with mutations in
    the gyrA gene leading to the amino acid changes Ser83Phe and Asp87Asn.
    Conclusions: Resistance was common among Vietnamese Salmonella isolates from different sources. Legislation to enforce
    a more prudent use of antibiotics in both human and veterinary medicine should be implemented by the authorities in
    Original languageEnglish
    Article numbere9440
    Number of pages8
    JournalPLoS One
    Issue number2
    Publication statusPublished - 2010


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