mecA、mecI和mecR1基因在耐甲氧西林凝固酶阴性葡萄球菌中的分布与变异

Distribution and Variation of mecA,mecI and mecR1 in Meticillin-resistant Coagulase Negative Staphylococci

目的检测126株临床分离的耐甲氧西林凝固酶阴性葡萄球菌中mecA、mecI和mecR1基因分布与变异。方法采用多重PCR的方法,使用11条特异性的引物,分别检测mecA、mecI和mecR1基因最易发生突变的位点。结果126株临床分离的耐甲氧西林凝固酶阴性葡萄球菌均检测到mecA基因,阳性率100.0%,3株发现在与引物P1退火的区域发生突变,2株在mecA基因的内切酶ClaI区域发生变异,39株未发现在mecI和mecR1基因内发生突变,42株发现在mecR1基因的跨膜区(PB domain)发生突变,mecR1基因青霉素结合区发生突变18株,27株发生mecI基因的缺失,9株同时发生mecI和mecR1基因缺失。结论研究结果表明,mecA基因在耐甲氧西林凝固酶阴性葡萄球菌中比较稳定,较少发生突变,mecI和mecR1基因容易发生缺失,检测临床分离的耐甲氧西林凝固酶阴性葡萄球菌中mecA、mecI和mecR1基因的分布和变异对于正确分析和解释耐药性的结果、追踪耐药菌株来源有重要意义。

OBJECTIVE To investigate the variation and distribution of mecA, mecI and mecR1 in 126 clinical isolates of meticillin-resistant coagulase negative staphylococci（MRCNS）. METHODS The multiplex PCR was used to determinee the distribution, alteration and deletion in the mecA, mecI and mecR1 genes with 11 sets of primers and 7 reactions. RESULTS All of the MRCNS isolates were mecA-positive, 3 strains showed alteration of the specific region with complementarity to the annealing site of primer P1, while 2 strains showed the alteration at the ClaI restriction site of the mecA gene. Thirty-nine of the MRCNS clinical isolates carried the whole regulator region without alterations in the binding sites for the primer used. 18 isolates showed a deletion of the PB domain of the mecR1 gene, 27 isolates lacked the regulator gene mecI. Nine isolates had deletions of both regulator genes. CONCLUSIONS The mecA gene is highly conserved among the clinical MRCNS isolates, but mecI and meeR1 have more deletions. This results might explain the different expression of resistance to meticillin and be helpful to trace the origin of the MRCNS strains