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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 of plasmid-mediated quinolone resistance genes qnrA, aac (6 ’) - Ib-cr in clinical strains of Enterobacteriaceae in Tianjin and its mechanism of drug resistance. Methods A total of 116 strains of Enterobacteriaceae were collected from 8 top three hospitals in Tianjin, including 77 strains of Escherichia coli, 24 strains of Enterobacter cloacae and 15 strains of Klebsiella pneumoniae (CPLX, MIC ≥ 4μg / ml) Lebacterium bacteria. The qnrA gene of all clinical strains was screened by PCR and the aac (6 ’) - Ib was tested against Escherichia coli. The drug susceptibility of the strains was tested by agar dilution method. The DNA sequence of aac (6’) - cr gene variants; conjugation delivery assay to explore bacterial plasmid-mediated resistance transmission. Results No qnrA gene was found in 116 quinolone-resistant Enterobacteriaceae strains. A total of 77 strains of ciprofloxacin-resistant Escherichia coli were identified as aac (6 ’) - Ib, 10 strains were resistant to methycline, 4 were sensitive and 1 were sensitive. The aac (6 ’) - Ib amplified products of 6 strains with different kanamycin resistance phenotype were selected and sequenced. The results showed that 5 strains The bacteria carried aac (6 ’) - Ib-cr at position 223 (T → C or T → A) and 454 (G → T) The resistance to quinolones and aminoglycosides is partially transmitted to the recipient strain. Conclusion The qnrA gene is very rare in 116 Enterobacteriaceae clinical isolates in Tianjin. For the first time, aac (6 ’) - Ib-cr-mediated quinolone resistance was found in Tianjin.