Phenotypic and molecular characteristics of drug resistant S. Typhi (n = 18) isolates from Kolkata during 2009–2013.

Abbreviations used: MDR, multidrug resistant; ND, not done; A, ampicillin; C, chloramphenicol; Q, co-trimoxazole; T, tetracycline; S, streptomycin; Na, nalidixic acid; Ci, ciprofloxacin; Of, ofloxacin; Le, levofloxacin; Ac, amoxicillin/clavulanic acid.aall isolates were negative for blaOXA, blaSHV and sul3 genes by PCR.bpossessed dfrA7 gene cassette as determined by sequencing of 750 bp PCR amplicon.cplasmid type: IncN; tetA was positive, but tetB was negative by PCR; transfer of tetA, sul1, dfrA15 and aadA1 genes by conjugation.dgene cassette could not be determined by sequencing of 1.6 kb PCR amplicon.所用缩写说明： MDR（multidrug resistant，多重耐药）；ND（not done，未检测）；A（ampicillin，氨苄西林）；C（chloramphenicol，氯霉素）；Q（co-trimoxazole，复方新诺明）；T（tetracycline，四环素）；S（streptomycin，链霉素）；Na（nalidixic acid，萘啶酸）；Ci（ciprofloxacin，环丙沙星）；Of（ofloxacin，氧氟沙星）；Le（levofloxacin，左氧氟沙星）；Ac（amoxicillin/clavulanic acid，阿莫西林克拉维酸）。 a. 经聚合酶链式反应（Polymerase Chain Reaction，PCR）检测，所有分离株的blaOXA、blaSHV及sul3基因均呈阴性。 b. 对750 bp的PCR扩增产物进行测序分析，确认其携带dfrA7基因盒。 c. 质粒类型为IncN型；经PCR检测，tetA基因呈阳性，tetB基因呈阴性；通过接合可转移tetA、sul1、dfrA15及aadA1基因。 d. 对1.6 kb的PCR扩增产物进行测序后，无法确定其基因盒类型。