1. Characteristics of Resistance Mechanisms and Molecular Epidemiology of Fluoroquinolone-Nonsusceptible Salmonella enterica Serovar Typhi and Paratyphi A Isolates from a Tertiary Hospital in Dhaka, Bangladesh.
- Author
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Okanda T, Haque A, Ehara T, Huda Q, Ohkusu K, Miah RA, and Matsumoto T
- Subjects
- Anti-Bacterial Agents pharmacology, Bangladesh epidemiology, Cross Infection microbiology, DNA Gyrase genetics, Drug Resistance, Multiple, Bacterial, Fluoroquinolones pharmacology, Humans, Levofloxacin pharmacology, Microbial Sensitivity Tests, Molecular Epidemiology, Multilocus Sequence Typing, Mutation genetics, Quinolones pharmacology, Tertiary Care Centers, Drug Resistance, Bacterial genetics, Salmonella Infections epidemiology, Salmonella Infections microbiology, Salmonella enterica drug effects, Salmonella paratyphi A drug effects, Typhoid Fever epidemiology, Typhoid Fever microbiology
- Abstract
The aim of this study was to characterize the fluoroquinolone (FQ) resistance mechanism of Salmonella enterica serovar Typhi and Paratyphi A in Bangladesh. Salmonella Typhi isolates were classified into sequence type (ST) 1, ST2, and ST2209 and Salmonella Paratyphi A isolates were classified into ST85 and ST129. The most common STs of the FQ-nonsusceptible strain were ST1 (44.4%) and ST129 (66.6%). Thirty-nine percent of Salmonella Typhi isolates were multidrug resistant, and these were all ST1, which is the type prevalent in the Indian subcontinent. Although plasmid-mediated quinolone resistance genes were not detected in any of the tested strains, single and double mutations were identified in the quinolone resistance-determining region (QRDR). The most common QRDR mutation was GyrA_Ser83Phe (66.7% for Salmonella Typhi and 100% for Salmonella Paratyphi A). Treatment with an efflux pump inhibitor resulted in susceptibility of the strains to levofloxacin. All isolates demonstrated 100% susceptibility to ceftriaxone, azithromycin, and carbapenem. Our results suggest that mutations in gyrase A and enhancement of efflux pump activity are responsible for the resistance to FQs; in particular, the AcrAB-TolC efflux pump may be an important resistance factor for levofloxacin. To control the spread of FQ-nonsusceptible Salmonella Typhi, intensive surveillance in endemic areas, including Bangladesh, and effective infection control are necessary.
- Published
- 2018
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