志贺菌属对氟喹诺酮类药物耐药机制的研究

目的 研究志贺菌属对氟喹诺酮类药物的耐药机制。方法 从临床上收集志贺菌１５７株,进行药敏试验、利血平逆转试验、Ｒ质粒接合试验和细菌内诺氟沙星聚积的测定。对其中８株耐药菌、１株敏感菌和１株福氏标准菌的基因５＾１－末端编码区进行聚合酶链瓜 增并克隆和序列分析。结果 诺沙星耐药菌的Ｒ质粒接合试验阳性率为５１．２％,Ｒ质粒不能传递对氟喹诺酮类药物的耐药物,利血有降低氟喹诺酮类药物对志贺菌的最低抑菌浓度值,

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. CONCLUSION: The mutations of gyrA gene were implicated in the resistance of Shigellae to fluoroquinolones.