title: [A study on the mechanism of the resistance of Shigellae to fluoroquinolones].
abstract: OBJECTIVE
  To study the mechanism of the resistance of Shigellae to fluoroquinolones.
  
  
  METHODS
  A total of 157 clinical isolates were collected. Antibiotic susceptibility testing, reserpine reverse reaction and plasmid conjugation experiment were performed. Accumulation of norfloxacin by shigellae was determined. The N-terminal coding region of gyrA gene was amplified by polymerase chain reaction (PCR), cloned and sequenced in eight fluoroquinolone-resistant isolates and one fluoroquinolone-sensitive isolate as well as in Shigella 51573 (the standard strain).
  
  
  RESULTS
  The positive rate of norfloxacin-resistant isolates was 51.2% in the R plasmid conjugation experiment. R plasmid could not mediate resistance to fluoroquinolones. Reserpine could not decrease the minimum inhibition concentration of fluoroquinolones to Shigellae. Norfloxacin uptake by fluoroquinolone-resistant isolates was the same as that by the sensitive one. DNA sequence analysis of gyrA gene from fluoroquinolone-resistant isolates revealed five point mutations that resulted in amino acid change: Gly-81-->Ser, Ser-83-->Leu, Asp-87-->Asn, Asp-87-->Gly, Met-92-->Lys.
  
  
  CONCLUSIONS
  The mutations of gyrA gene were implicated in the resistance of Shigellae to fluoroquinolones.
authors.affiliation: Department of Infectious Diseases, The First Affiliated Hospital, Zhejiang Medical University, Hangzhou 310003.
authors.forename: J
authors.initials: J
authors.lastname: Ding
authors.forename: Y
authors.initials: Y
authors.lastname: Ma
authors.forename: Z
authors.initials: Z
authors.lastname: Gong
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024841:Fluoroquinolones / Q000494:pharmacology*; D005798:Genes, Bacterial; D008826:Microbial Sensitivity Tests; D009154:Mutation; D011815:R Factors / Q000235:genetics; D012760:Shigella / Q000187:drug effects* / Q000235:genetics*
chemical_list: D000890:Anti-Infective Agents; D024841:Fluoroquinolones