Molecular epidemiology and resistance of oxacillin susceptible methicillin-resistant Staphylococcus aureus isolates

目的：分析苯唑西林敏感甲氧西林耐药的金黄色葡萄球菌（ MRSA ）的耐药性及分子流行病学特点。方法用琼脂二倍稀释法测定苯唑西林敏感头孢西丁耐药的金黄色葡萄球菌菌株的敏感性，聚合酶链式反应（ PCR）法检测金黄色葡萄球菌特异性nuc基因，多重PCR检测mecA、mecC以及杀白细胞素pvl基因；并进行SCCmec和spa分型。结果从288株甲氧西林耐药的金黄色葡萄球菌检测到14株苯唑西林敏感头孢西丁耐药的菌株，检出率为4.9％。菌株主要来自分泌物标本（50％，7／14），其次为血标本（28.6％，4／14）。14株菌株对庆大霉素，阿米卡星，利福平，复方新诺明的敏感率在90％以上；对喹诺酮类的敏感率约在80％；对四环素，氯霉素的敏感率均为28.6％；对红霉素，阿奇霉素，克林霉素的耐药率在90％以上。14株细菌均为金黄色葡萄球菌，均含有mecA基因，均不含mecC基因；pvl基因检出率为78.6％（11／14）。 SCCmecⅤ－spat437是最常见分型，占42.9％（6／14）。结论2011－2012年我国苯唑西林敏感MRSA的分子分型主要是SCCmecⅤ－spat437型，耐药表型上除大环内酯类、克林霉素、四环素、氯霉素外，对其余抗菌药多表现为敏感。Objective To understand the resistance, molecular charac-teristics of oxacillin susceptible methicillin-resistant Staphylococcus au-reus ( OS-MRSA) strains isolated 2011-2012 in China.Methods A total of 297 methicillin -resistant Staphylococcus aureus ( MRSA ) were collected in the Ministry of Health National Antimicrobial Resistance Sur-veillance Net program and the susceptibility test were performed by agar dilution method.All the oxacillin-susceptible MRSA strains were con-firmed to be Staphylococcus aureus by detecting nuc gene.The molecular typing methods included SCCmec and spa typing.Results A total of 14 isolates ( 4.9%) were oxacillin susceptible methicillin-resistant Staphy-lococcus aureus among 288 MRSA isolates and most of them were from se-cretion (50%, 7/14) and blood (28.6%, 4/14).The susceptibility rate to gentamicin, amikacin, rifampicin and trimethroprim/sulfamethox-azole was more than 90% and the rate to quinolones, tetracycline and chloramphenicol was about 80%, 28.6%, 28.6%, respectively.Moreo-ver, the resistance rate to erythromycin, azithromycin and clindamycin was more than 90%.PCR revealed that 14 isolates were Staphylococcus aureus and mecA positive and the most predominant clone was SCCmecⅤ-spat437 (42.9%,6/14).Conclusion The most predominant clone of the OS-MRSA isolates in China was SCCmecⅤ-spat437; most of OS-MRSA isolates were susceptible to the majority of antibacterial agents except macrolides, tetracycline and chloramphenicol.国家科技重大专项课题基金资助项目中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)11912-9153