志贺菌喹诺酮类耐药株gyrA和parC基因突变研究

Mutations of the gyrA and parC genes of quinolone-resistant bacteria of Shigella spp

目的检测志贺菌对喹诺酮类药的耐药情况,指导临床合理用药;探讨志贺菌喹诺酮类耐药株gyrA和parC基因的突变,分析GyrA和ParC氨基酸改变与喹诺酮类耐药的关系。方法 2010~2012年从宿州市3家综合性医院收集志贺菌76株,进行分离培养和血清型鉴定;采用K-B纸片法进行药物敏感试验;采用PCR方法检测志贺菌喹诺酮耐药决定区（QRDR）相关gyrA和parC基因,并挑选部分PCR产物进行DNA测序分析。结果收集的76株志贺菌中福氏志贺菌74株（占97.4%）,宋内志贺菌2株（占2.6%）;药敏结果显示志贺菌耐药情况严重,其中对阿莫西林耐药率最高,达100%;对头孢噻肟耐药率最低,为6.5%。对gyrA基因的序列分析发现3个导致氨基酸改变的基因点突变：Ser83→Leu,Asp87→Gly及His211→Tyr;对parC基因序列分析发现2个导致氨基酸改变的基因点突变：parC Ser80→Ile和Asp197→Asn。结论宿州市志贺菌感染仍以福氏志贺菌为优势菌群,且耐药严重,临床治疗志贺菌感染可优先选择头孢噻肟。志贺菌属对喹诺酮类药物产生耐药性与gyrA和parC基因突变有关,GyrA His211→Tyr和ParC Asp197→Asn氨基酸变异与喹诺酮类耐药的关系需进一步研究。

Objectives To investigate the quinolone-resistant strains of Shigellaspp.collected in the City of Suzhou in order to provide information for rational selection of antibiotics,to identify mutations of the gyrAand parCgenes in quinolone-resistant Shigellaspp.,and to analyze the relationship between quinolone resistance and amino acid alterations in GyrAand ParC. Methods Seventy-six strains of Shigella bacteria were collected from 3general hospitals in Suzhou,Anhui in China,from 2010to 2012for bacterial identification.A drug susceptibility test was performed using the K-B method and quinolone-resistant gyrAand parCgenes of Shigellalinked to the decision area（QRDR）were detected with apolymerase chain reaction（PCR）.The PCR products were subsequently subjected to DNA sequencing. Results Of76strains of Shigella,74（97.4%）were identified as Shigella flexneri and 2（2.6%）were identified as S.sonnei.The susceptibility test indicated that Shigellais highly resistant to amoxicillin,with resistance as high as 100%.Shigellahad the lowest resistance to cefotaxime（6.5%）.DNA sequence analysis of genes fromShigellaspp.indicated that quinolone-resistant strains had 3mutations resulting in amino acid changes：Ser83→Leu,Asp87→Gly,and His211→Tyr.Two amino acid residue alterations were observed in the parCgene：Ser80→Ile and Asp197→Asn. Conclusion S.flexneri remains a dominant species in the City of Suzhou.Cefotaxime is the drug of choice for clinical treatment of Shigella-related infection.The resistance of Shigellaspp.to quinolones is related to mutations of the gyrAand parCgenes.The relationship between the amino acid variations GyrA His211→Tyr and ParC Asp197→Asn and quinolone resistance needs to be investigated further.