Department of Microbiology, General Hospital of PLA, Beijing, China.
J Antimicrob Chemother. 2010 Mar;65(3):453-9. doi: 10.1093/jac/dkp478. Epub 2010 Jan 7.
The categories of recognized transferable quinolone resistance determinants have been increasing sharply. The rapid horizontal transfer of these quinolone resistance genes has caused concern since they bring new dissemination possibilities for quinolone resistance.
In total, 579 clinical Escherichia coli isolates were subjected to antimicrobial susceptibility testing, screening for qnr alleles, qepA and aac-(6')-Ib-cr by PCR amplification and DNA sequence analysis. Isolates containing transferable quinolone resistance determinants were further characterized by mutation analysis in the quinolone resistance determining regions (QRDRs) of GyrA and ParC, phylogenetic typing and PFGE to determine their genetic relatedness.
After PCR screening and sequence analysis, transferable quinolone resistance determinants were identified in 74 of 579 E. coli isolates (12.8%). The antimicrobial resistance profiles and phylogenetic groups differed between isolates containing different categories of transferable quinolone resistance determinant. Most of the isolates containing qepA alone were highly resistant to ciprofloxacin (MIC >or= 512 mg/L) and belonged to phylogenetic group D (22/25), while most of the isolates containing aac-(6')-Ib-cr alone belonged to phylogenetic group A (17/35) or D (16/35). Of 74 E. coli isolates containing transferable quinolone resistance determinants, 69 PFGE patterns and 19 clusters were identified.
The great genetic variation of E. coli hosts containing transferable quinolone resistance determinants demonstrated the high transmission capacity of these mechanisms. It is urgent to characterize and block their transmission routes in order that the utility of quinolones is preserved.
已识别的可转移喹诺酮类药物耐药决定因子的类别急剧增加。由于这些喹诺酮类耐药基因的快速水平转移为喹诺酮类耐药带来了新的传播可能性，因此引起了人们的关注。
对 579 株临床分离的大肠杆菌进行了药敏试验、qnr 等位基因、qepA 和 aac-(6')-Ib-cr 的 PCR 扩增和 DNA 序列分析。对携带可转移喹诺酮类药物耐药决定因子的菌株进一步通过喹诺酮类耐药决定区（QRDR）gyrA 和 parC 的突变分析、系统发生分型和 PFGE 对其遗传相关性进行了特征分析。
经 PCR 筛选和序列分析，在 579 株大肠杆菌分离株中发现了 74 株（12.8%）携带可转移喹诺酮类药物耐药决定因子。携带不同种类的可转移喹诺酮类药物耐药决定因子的分离株的药敏谱和系统发生群不同。单独携带 qepA 的分离株对环丙沙星的耐药率较高（MIC>或=512mg/L），且主要属于 D 组（22/25），而单独携带 aac-(6')-Ib-cr 的分离株主要属于 A 组（17/35）或 D 组（16/35）。在 74 株携带可转移喹诺酮类药物耐药决定因子的大肠杆菌分离株中，共鉴定出 69 种 PFGE 图谱和 19 个克隆群。
携带可转移喹诺酮类药物耐药决定因子的大肠杆菌宿主的遗传变异较大，表明这些机制具有很强的传播能力。迫切需要对其传播途径进行特征分析和阻断，以保持喹诺酮类药物的效用。
