title: [Mutations of gyrA gene and parC gene in fluoroquinolone-resistant Escherichia coli isolates from sporadic diarrheal cases].
abstract: We studied 107 isolates of Escherichia coli O153 from sporadic diarrhea cases in Fukui, Toyama, Aichi, and Saga prefectures from 1991 to 2005 for antimicrobial susceptibility and mechanisms of fluoroquinolone resistance, based on standard disk diffusion. Of 12 drugs tested, ampicillin displayed resistance to 72.9% of isolates, streptomycin to 48.6%, tetracycline to 46.7%, sulfisoxazole to 46.7%, trimethoprim/sulfamethoxazole to 29.9%, nalidixic acid (NA) to 29.9%, and ciprofloxacin (CPFX) to 24.3%. Ten of 32 isolates resistant to 3-6 drugs and 16 of 18 isolates resistant to 7-10 drugs were resistant both to NA and CPFX. Mutations of amino acid in quinolone resistance-determining regions of gyrA and parC genes were detected in 24 isolates resistant both to NA and CPFX, and in 1 isolate resistant to NA. The former possessed a combination of double substitution (S83L and D87L) in GyrA and a single substitution (S80I) in ParC. Some 12 of 24 isolates possessed another single substitution (E84V or E84G or A108T) in ParC. The 25 isolates were classified into 4 types as follows. 1 isolate as type 1: GyrA (S83L) and ParC (S80I); 12 isolates as type 2: GyrA (S83L and D87N) and ParC (S80I); 8 isolates as type 3: GyrA (S83L and D87N) and ParC (S80I and E84G/S80R and E84V); and 4 isolate as type 4: GyrA (S83L and D87N) and ParC (S80I and A108T). In the relationship between amino acid mutations and minimal inhibitory concentrations (MIC) of fluoroquinolone, MICs of CPFX, ofloxacin, and norfloxacin showed 1microg/mL, 2microg/mL and 8microg/mL in type 1; 8 approximately 32microg/mL, 8 approximately 32microg/mL and 16 approximately 256microg/mL in type 2; and 32 approximately 256microg/mL' 32 approximately 128microg/mL and 128-->512microg/ mL in types 3 and 4. These results suggest that most of multiple-antimicrobial-resitant E. coli O153 isolates from sporadic diarrhea cases were resistant to fluoroquinolones and possessed mutations at gyrA and parC genes associated with fluoroquinolone resistance.
authors.affiliation: Fukui Prefectural Institute of Public Health and Enviomental Science.
authors.forename: Fubito
authors.initials: F
authors.lastname: Ishiguro
authors.forename: Miho
authors.initials: M
authors.lastname: Toho
authors.forename: Mitsugu
authors.initials: M
authors.lastname: Yamazaki
authors.forename: Seiko
authors.initials: S
authors.lastname: Matsuyuki
authors.forename: Kazuo
authors.initials: K
authors.lastname: Moriya
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tanaka
authors.forename: Junko
authors.initials: J
authors.lastname: Isobe
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Kyota
authors.forename: Michio
authors.initials: M
authors.lastname: Muraoka
mesh_terms: D027081:DNA Gyrase / Q000235:genetics*; D027101:DNA Topoisomerase IV / Q000235:genetics*; D003967:Diarrhea / Q000382:microbiology*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D024841:Fluoroquinolones / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation
chemical_list: D024841:Fluoroquinolones; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase