[A study on the mechanism of the resistance of Shigellae to fluoroquinolones].
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.
Ding
J
J
Department of Infectious Diseases, The First Affiliated Hospital, Zhejiang Medical University, Hangzhou 310003.
Ma
Y
Y
Gong
Z
Z
Chen
Y
Y
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*
D000890:Anti-Infective Agents; D024841:Fluoroquinolones