志贺菌对喹诺酮类药物耐药分子机制的研究

目的 研究志贺菌对喹诺酮类药物耐药性及其耐药基因gyrA和parC的变异。方法对73株临床分离的志贺菌及标准株51573进行吡哌酸(PI)、氧氟沙星(OFL)、诺氟沙星(NOR)、环丙沙星(CIP)4种药物的药敏试验,对其DNA旋转酶gyrA基因、拓扑异构酶ⅣparC基因N末端编码区分别进行聚合酶链反应(PCR)扩增后,对grA基因进行限制性片段长度多态性(RFLP)分析,对parC基因进行RFLP及单链构象多态性(SSCP)分析。结果 标准株51573对4种喹诺酮类药物均敏感;73株临床分离的志贺菌属细菌对PI、CIP、NOR、OFL的耐药率分别为79.5％、60.3％、41.1％和36.9％;67株(91.8％)菌株对喹诺酮类药物敏感性降低,其中gyrA基因突变率为91％,parC基因突变率为7.5％,6株临床敏感株及标准株51573均未检测出以上两基因突变。结论 志贺菌对喹诺酮类药物耐药严重;靶基因突变是其耐喹诺酮类药物的主要机制之一,以DNA旋转酶gyrA基因突变为主,拓扑异构酶ⅣparC基因突变次之。

Study on the molecular mechanism of quinolone resistance in Shigellae spp.

Objective To study the resistance and its mechanism of Shigellae spp. to quinolones. Methods Seventy--three clinical isolates were collected. Susceptibility tests of pipemidic adcid (PI), ofloxacin (OFL), norfloxacin (NOR), and ciprofloxacin (CIP) were performed in all clinical isolates and Shigella 51573. The N--terminal coding region of gyrA and parC were amplified by polymerase chain reaction (PCR) repectively. Restriction fragment length polymorphism (RFLP) was applied to all PCR procucts of gyrA and parC, and single strand conformational polymorphism analysis (SSCP) was also applied to PCR procucts of parC. Results The resistance rates for all the Shigella spp. to PI, CIP, NOR and OFL were 79. 5 %, 60. 3 %, 41. 1% and 36. 9 %. Sixty--seven strains (91. 8 %) were quinolone--reduced- sensitive isolates, in which 61 strains (91 %) were found carrying mutations in gyrA with 5 strains (7. 5%) found carrying mutations in parC. No mutation was found in 6 quinolone--sensitive isolates or Shigella 51573. Conclusion The Shigella spp. had high resistance rates to quinolones. The target gene mutations which were mainly found in gyrA and secondarily in parC, played an important role in the quinolone--resistance in Shigella spp.