title: Antimicrobial resistance in Salmonella enterica Serovar Typhi isolates from Bangladesh, Indonesia, Taiwan, and Vietnam.
abstract: 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 were 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 isolates from Vietnam but in only 15% of MDR isolates from Bangladesh. Resistance genes in the majority of MDR S. Typhi isolates from Bangladesh should reside in the chromosome. Among the isolates from Bangladesh, 82% and 40% were resistant to various 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 fluoroquinolones. Intensive surveillance is necessary to monitor the spread of chromosome-mediated MDR and fluoroquinolone-resistant S. Typhi emerging in Bangladesh.
authors.affiliation: Centers for Disease Control, Taichung, Taiwan nipmcsc@cdc.gov.tw.
authors.forename: Chien-Shun
authors.identifier: http://orcid.org/0000-0003-3674-1030
authors.initials: CS
authors.lastname: Chiou
authors.affiliation: National Health Research Institutes, Zhunan, Taiwan.
authors.forename: Tsai-Ling
authors.initials: TL
authors.lastname: Lauderdale
authors.affiliation: National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.
authors.forename: Dac Cam
authors.initials: DC
authors.lastname: Phung
authors.affiliation: National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Haruo
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Centers for Disease Control, Taichung, Taiwan.
authors.forename: Jung-Che
authors.initials: JC
authors.lastname: Kuo
authors.affiliation: Centers for Disease Control, Taichung, Taiwan.
authors.forename: Pei-Jen
authors.initials: PJ
authors.lastname: Wang
authors.affiliation: Centers for Disease Control, Taichung, Taiwan.
authors.forename: Yen-Yi
authors.initials: YY
authors.lastname: Liu
authors.affiliation: Centers for Disease Control, Taichung, Taiwan.
authors.forename: Shiu-Yun
authors.initials: SY
authors.lastname: Liang
authors.affiliation: National Health Research Institutes, Zhunan, Taiwan.
authors.forename: Pei-Chen
authors.initials: PC
authors.lastname: Chen
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001459:Bangladesh; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics; D002939:Ciprofloxacin / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D005838:Genotype; D006801:Humans; D007214:Indonesia; D008826:Microbial Sensitivity Tests; D009268:Nalidixic Acid / Q000494:pharmacology; D010802:Phylogeny; D010957:Plasmids / Q000187:drug effects / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D012485:Salmonella typhi / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D013624:Taiwan; D014435:Typhoid Fever / Q000188:drug therapy / Q000382:microbiology; D014744:Vietnam
chemical_list: D000900:Anti-Bacterial Agents; D002352:Carrier Proteins; D009268:Nalidixic Acid; D002939:Ciprofloxacin