title: Resistance to fluoroquinolones by the combination of target site mutations and enhanced expression of genes for efflux pumps in Shigella flexneri and Shigella sonnei strains isolated in Korea.
abstract: Among 5938 clinical Shigella spp. isolates, two S. flexneri strains were isolated as those resistant to fluoroquinolones based on the MICs of the following antibiotics: ciprofloxacin, norfloxacin, ofloxacin, sparfloxacin and levofloxacin. S. flexneri 021787 had three substitutions, one in GyrA (Ser83Leu) and two in ParC (Ser80Ile and Arg91Gln). S. flexneri 021895 had four substitutions, two in GyrA (Ser83Leu and Asp87Gly) and two in ParC (Ser80Ile and Arg91Gln). The increased susceptibility of S. flexneri 021787 and S. flexneri 021895 to ciprofloxacin, norfloxacin and ofloxacin in the presence of the uncoupler carbonyl cyamide-m-chlorophenyldrazone implied that energy-dependent active efflux pumps contributed to the resistance against fluoroquinolones. Both S. flexneri 021787 and S. flexneri 021895 were also induced to express tolC (encoding a resistance-nodulation-division transporter), mdfA (encoding a major facilitator superfamily transporter), and ydhE (encoding a multidrug and toxic compound extrusion transporter) in the presence of ciprofloxacin. Thus, these results indicated that chromosome-mediated fluoroquinolone resistance of S. flexneri 021787 and S. flexneri 021895 resulted from the combination of target site mutations and enhanced expression of genes encoding efflux pumps.
authors: Division of Enteric Bacterial Infections, Center for Infectious Disease, National Institute of Health; and Institute of Global Environmental and Department of Biology, Kyung Hee University, Seoul, Korea.
authors: J-Y
authors: JY
authors: Kim
authors: S-H
authors: SH
authors: Kim
authors: S-M
authors: SM
authors: Jeon
authors: M-S
authors: MS
authors: Park
authors: H-G
authors: HG
authors: Rhie
authors: B-K
authors: BK
authors: Lee
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D027081:DNA Gyrase / Q000235:genetics / Q000378:metabolism; D027101:DNA Topoisomerase IV / Q000235:genetics / Q000378:metabolism; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004405:Dysentery, Bacillary / Q000382:microbiology; D024841:Fluoroquinolones / Q000494:pharmacology*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007723:Korea; D008826:Microbial Sensitivity Tests; D009154:Mutation; D012763:Shigella flexneri / Q000187:drug effects* / Q000235:genetics; D012764:Shigella sonnei / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D024841:Fluoroquinolones; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase