耐甲氧西林金黄色葡萄球菌的主动外排系统基因qacA/B的检测及其意义

目的：应用半巢氏聚合酶链式反应（PCR）技术检测临床分离耐甲氧西林金黄色葡萄球菌（MRSA）主动外排系统qac基因，了解qac基因的存在状况。方法：根据MRSA主动外排系统qacA和qacB基因序列设计引物，采用半巢氏PCR法对中南大学3所附属医院2006年8月至2008年3月临床分离的80株MRSA分别扩增qacA/B和qacB基因，并进行序列分析。结果：在80株受检MRSA中，检出qacA/B基因19株，检出率23.75%；qacB基因18株，检出率22.5%。序列分析显示，qac基因与qacA的参考序列 (X56628)98%相同，与参考序列qacB（AF535087）97%相同。结论：半巢氏PCR法可成功检测MRSA的主动外排系统qac基因。qac基因阳性株在临床分离的MRSA中占有较高的比例，可能与其多重耐药有关。

Identification of active efflux system gene qacA/B in methicillin-resistant Staphylococcus aureus and its significance

ObjectiveTo detect the active efflux gene qac gene in methicillin-resistant Staphylococcus aureus (MRSA) by hem-nested polymerase chain reaction (PCR) and to learn the carrier condition of qac gene.MethodsThe active efflux gene qacA/B and qacB of 80 strains MRSA isolated from clinical specimens from Aug 2006 to March 2008 were amplified in vitro by hem-nested PCR with the primers designed by computers based on qac information of Genbank, and the PCR fragments were sequenced and analyzed.ResultsWe detected qacA/B in 19 out of the 80 MRSA strains (23.75%) and qacB in 18 out of the 80 MRSA strains (22.5%). Compared with sequences of qacA (NO.X56628) and qacB（NO.AF535087) in the Genbank, 98% and 97% were identical, respectively.ConclusionThe active efflux gene qac gene in MRSA is detected by hem-nested PCR. The proportion of qac gene positive strains is high in clinical practice, which is related to its multi-antibiotic resistance.