上海地区肺炎链球菌对氟喹诺酮类的敏感性及其喹诺酮耐药决定区突变研究

目的了解上海地区临床分离肺炎链球菌对氟喹诺酮类等抗菌药物的敏感性，并对氟喹诺酮类敏感菌株的喹诺酮耐药决定区（QRDR）突变进行初步研究。方法收集上海地区部分医院2004-2005年共176株肺炎链球菌临床分离株，用琼脂稀释法测定环丙沙星、左氧氟沙星、加替沙星和莫西沙星等15种抗菌药物的抗菌活性，并选取部分左氧氟沙星敏感肺炎链球菌菌株进行QRDRPCR扩增、测序。结果176株受试菌株中．PSSP、PISP和PRSP各占48．9％、47．1％和4．0％，受试菌株对环丙沙星、左氧氟沙星、加替沙星和莫西沙星敏感率均为100％。QRDR的扩增测序结果发现，20株左氧氟沙星MIC1～2mg／L的敏感菌株中，19株的parC、parE基因上已存在不同程度的氨基酸突变．包括ParC：Phe 105→Leu／Asp136→Tyr，Pare：Asp435→AsnjIle460→ValjAsn477→Lys．而在gyrA、gyrB基因上仅发现点突变，未导致相关氨基酸突变。结论上海地区未发现氟喹诺酮类耐药肺炎链球菌临床分离株，但左氧氟沙星MIC1～2mg／L的敏感株中已发现QRDR一级突变现象，突变的基因位点均见于parC、pare基因。

Fluoroquinolone susceptibility and quinolone resistance determining region mutations in Streptococcus pneumoniae isolates from Shanghai

Objective To investigate the antimicrobial susceptibility of S. pneumoniae isolates from Shanghai to fluoroquinolones and other antibiotics, and explore the quinolone resistance determining region （QRDR） mutations in fluoroquinolone-susceptible S. pneumoniae. Methods Susceptibility testing was performed for 176 S. pneumoniae isolates collected in Shanghai during 2004-2005 by agar dilution method as described by Clinical and Laboratory Standards Institute （CLSI）. Selected levofloxacin-susceptible S. pneumoniae isolates were analyzed by PCR and sequencing to understand the mutations in QRDR, including parC, parE, gyrA and gyrB genes. Results Of the 176 clinical S. pneumoniae isolates, 48.9%, 47.1% and 4.0% were identified as penicillin-susceptible （PSSP）, penicillin-intermediate （PISP） and penicillin-resistant （PRSP）, respectively. All the isolates were susceptible to ciprofloxacin, levofloxacin, gatifloxacin and moxifloxacin. Of the 20 levofloxacin-susceptible isolates with levofloxaein MIC 1-2 mg/L, 19 showed ParE： Ile460→Val. Some strains had additional substitution of ParE： Asp435→Asn/Asn 477→Lys and/or ParC： Phe 105→Leu/Asp 136→Tyr. Only point mutation was found in gyrA and gyrB genes. None of the isolates showed amino acid substitution in GyrA or GyrB. Conclusions The prevalence of penicillin nonsusceptible S. pneumoniae is high in Shanghai. No S. pneumoniae isolate was found resistant to fluoroquinolones, but first-step QRDR mutations （in parE or parC genes） are identified in levofloxacin-susceptible isolates （MIC 1-2 mg/L）.