摘要
目的了解天津地区肠杆菌科临床株中质粒介导的喹诺酮类耐药基因 qnrA、aac(6′)-Ib-cr 的分布并研究其耐药机制。方法从天津地区8家三甲医院收集环丙沙星耐药(CPLX,MIC≥4μg/ml)的肠杆菌科菌株共116株,包括77株大肠埃希菌、24株阴沟肠杆菌、15株克雷伯菌属细菌。应用 PCR 方法筛查所有临床株的 qnrA 基因,并对大肠埃希菌进行 aac(6′)-Ib 的检测;琼脂稀释法测菌株的药敏情况;DNA 测序检测 aac(6′)-Ib-cr 基因变异体;接合传递试验方法探讨细菌质粒介导的耐药性传递。结果 116株喹诺酮类耐药的肠杆菌科临床株中未发现 qnrA 基因阳性株;77株环丙沙星耐药的大肠埃希菌15株检出 aac(6′)-Ib,其中对卡那霉素耐药10株、中敏4株、敏感1株;选出对卡那霉素耐药表型不同的6株菌的 aac(6′)-Ib 扩增产物进行测序,结果表明5株菌在第223位(T→C或 T→A)和454位(G→T)发生变异,均携带 aac(6′)-Ib-cr;6株测序菌株中4株接合传递成功,临床株对喹诺酮类和氨基糖甙类的耐药性部分传递给了受体株。结论 qnrA 基因在天津地区116株肠杆菌科临床株中甚为罕见;首次在天津发现 aac(6′)-Ib-cr 介导的喹诺酮类耐药。
Objective To investigate the distribution and mechanism of plasmid-mediated quinolone resistance of clinical isolates in Enterobacteriaceae in Tianjin. Methods A total of 116 clinical isolates resistant to ciprofloxacin （77 isolate of E. coli, 24 isolates of Aerobacter cloacae, and 15 isolates of Klebsiella） in Enterobacteriaceae were collected from eight hospitals in Tianjin. The qnrA gene was detected for all the clinical isolates and aac（6＇）-Ib gene was detected for E. coli by PCR. Antimicrobial susceptibility test was performed by agar dilution test. DNA sequencing was used for identification of aac （ 6＇）-Ib-cr. Conjugation experiment was performed to determine ways of transmission of resistance. Results None of the clinical isolates in 116 isolates harbored a qnrA gene;The gene of aac（6＇）-Ib was present in 15 E. coli isolates, in which 10 isolates were resistant to kanamycin, 4 isolated were intermediate-intermediate to kanamycin and 1 isolate was susceptible to kanamycin. DNA sequencing for 6 isolates resistant to kanamycin showed that 5 of them contained nucleotide changes at positions 223 （T→C or T→A） and 454 （G→T）, indicating that they harbored aac （6＇）-Ib-cr gene. Conjugation experiments were successfully carried out in 4 isolates, and their resistance to quinolones and aminoglycosides was partly transmitted to the recipient strain. Conclusions The qnrA gene is especially rare in Enterobacteriaceae in Tianjin. This is the first report of aac（6＇）-Ib-cr mediated quinolone resistance in clinical isolates from Tianjin.
出处
《中华检验医学杂志》
CAS
CSCD
北大核心
2007年第11期1256-1259,共4页
Chinese Journal of Laboratory Medicine
