We characterized Salmonella enterica serovar Typhi isolates from Bangladesh, Indonesia, Taiwan and Vietnam to investigate their genetic relatedness and antimicrobial resistance. The isolates from Bangladesh and Vietnam were genetically closely related but distant from those from Indonesia and Taiwan. All but a few isolates from Indonesia and Taiwan were susceptible to all antimicrobials tested. The majority of isolates from Bangladesh and Vietnam were multidrug resistant (MDR) and belonged to the widespread haplotype H58 clone. IncHI1 plasmids were detected in all MDR S. Typhi from Vietnam but in only 15% of MDR isolates from Bangladesh. Resistance genes in the majority of MDR S. Typhi from Bangladesh should reside in the chromosome. Of the isolates from Bangladesh, 82% and 40% isolates were resistant to varying concentrations of nalidixic acid and ciprofloxacin, respectively. Several resistance mechanisms including alterations in gyrase A, the presence of QnrS and enhanced efflux pumps were involved in the reduced susceptibility and resistance to fluoroquinolone. Intensive surveillance is necessary to monitor the spread of the chromosome-mediated MDR and fluoroquinolone-resistant S. Typhi emerging in Bangladesh.
Date:
2014-11
Relation:
Antimicrobial Agents and Chemotherapy. 2014 Nov;58(11):6501-6507.
