A study on the mechanism of the resistance of Shigellae to fluoroquinolones
Ding, J.; Ma, Y.; Gong, Z.; Chen, Y.
Zhonghua Nei Ke Za Zhi 38(8): 550-553
1999
ISSN/ISBN: 0578-1426 PMID: 11798696 Document Number: 501899
To study the mechanism of the resistance of Shigellae to fluoroquinolones. 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). 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. The mutations of gyrA gene were implicated in the resistance of Shigellae to fluoroquinolones.