Han Dongqing, Huang Junwei, Shang Zhongbo, Xu Rong, Lou Yongliang, Chen Xiushu
School of Clinical Laboratory and Life Science, Institute of Microecology, Wenzhou Medical College, Wenzhou 325000, China.
Wei Sheng Wu Xue Bao. 2011 Apr;51(4):458-67.
To investigate co-existence of resistance genes (beta-lactamases, BLs, and aminoglycoside-modifying enzymes, AMEs) and their association with the genetic marker genes of Class I, II, III integrons carried by multiresistant Escherichia coli isolates.
We used VITEK-GNS to determine the susceptibility of 136 isolates to 14 antibiotics, disc agar diffusion test to confirm ESBL-producing isolates, PCR to analyze BLs, AMEs and integrons genes, conjugation and plasmids extraction to locate the methylase genes.
We found that 70.59% of the isolates produced ESBLs. They showed stronger resistance against 9 antibiotics than isolates without ESBLs in 14 antibiotics. PCR amplification showed that the positive rate of BLs, AMEs and qacEdelta1-sul1 was 96.32% , 100% and 94.12%, respectively, but Class II, III integrons genes were negative. Only one strain was oprD2 gene negative. 90.44% of the isolates were both positive for BLs and qacEdelta1-sul1 genes, and 94.12% for AMEs and qacEdelta1-sul1 genes, but there was no statistical significance. 90.44% of the isolates were all positive for the 3 genes. 12 strains carried 16S rRNA methylase genes including armA (2.21%), rmtB (7.35%) while rmtA, rmtC, rmtD were negative. The conjugation assay and plasmids mapping results showed that the methylase genes were located on the 23 kb plasmid, and the efficiency of transformation was 83.3%.
The results suggested that there was a tight correlation between the 3 genes (BLs, AMEs and qacEdelta1-sul1) and the incidences of multi-resistance of Escherichia coli, but there was no correlation of the incidence of multi-resistance with Class II, III integrons. 16S rRNA methylase genes harboured plasmids of -23 kb which transformed other isolates within the same strains efficiently.
研究多重耐药性大肠杆菌分离株中耐药基因（β-内酰胺酶、BLs，以及氨基糖苷类修饰酶、AMEs）的共存情况及其与Ⅰ类、Ⅱ类、Ⅲ类整合子遗传标记基因的相关性。
我们使用VITEK-GNS测定136株分离株对14种抗生素的敏感性，采用纸片琼脂扩散试验确认产超广谱β-内酰胺酶（ESBLs）的分离株，通过聚合酶链反应（PCR）分析BLs、AMEs和整合子基因，进行接合试验和质粒提取以定位甲基化酶基因。
我们发现70.59%的分离株产生ESBLs。在14种抗生素中，它们对9种抗生素的耐药性比不产ESBLs的分离株更强。PCR扩增显示，BLs、AMEs和qacEdelta1-sul1的阳性率分别为96.32%、100%和94.12%，但Ⅱ类、Ⅲ类整合子基因呈阴性。仅1株oprD2基因阴性。90.44%的分离株BLs和qacEdelta1-sul1基因均为阳性，94.12%的分离株AMEs和qacEdelta1-sul1基因均为阳性，但差异无统计学意义。90.44%的分离株3种基因均为阳性。12株携带了16S rRNA甲基化酶基因，包括armA（2.21%）、rmtB（7.35%），而rmtA、rmtC、rmtD为阴性。接合试验和质粒图谱分析结果显示，甲基化酶基因位于23 kb质粒上，转化效率为83.3%。
结果表明，3种基因（BLs、AMEs和qacEdelta1-sul1）与大肠杆菌多重耐药发生率密切相关，但多重耐药发生率与Ⅱ类、Ⅲ类整合子无关。携带16S rRNA甲基化酶基因的质粒大小约为23 kb，能在同一菌株内高效转化其他分离株。
