摘要：
目的 了解安徽地区儿童感染耐甲氧西林凝固酶阴性葡萄球菌(MRCNS)的耐药现状和葡萄球菌盒染色体mec(SCCmec)基因型分布及各基因型的耐药特点,以指导临床用药.方法 对安徽地区2010年至2014年每年9月临床送检的儿童感染凝固酶阴性葡萄球菌进行耐药表型筛选.利用PCR扩增mecA的方法收集MRCNS菌株.采用标准琼脂倍比稀释法测定MRCNS对16种抗生素的最低抑菌浓度(MIC)值,对万古霉素表型耐药菌株采用菌谱分析法和美国临床实验室标准化协会2013版推荐的含6 mg/L万古霉素脑心浸液琼脂稀释法进行鉴定,应用PCR检测其van基因,并对MRCNS进行SCCmec基因分型.结果 经表型筛选及mecA 基因检测双重方法共收集MRCNS 148株,包括表皮葡萄球菌、溶血葡萄球菌、人葡萄球菌及少数其他类型MRCNS,所占比例分别为44.59％(66/148株)、25.68％(38/148株)、19.59％(29/148株)及10.14％(15/148株).药敏分析显示MRCNS对青霉素、头孢哌酮、头孢噻肟、头孢曲松、哑胺培南、美罗培南耐药率均达100％,对红霉素、阿奇霉素、环丙沙星、克林霉素、庆大霉素、左氧氟沙星、利福平、氯霉素、替考拉宁、万古霉素的耐药率分别为92.57％,97.98％、83.78％、79.05％、43.24％,35.81％,24.32％、8.78％,2.03％、0.68％.发现l株异质性万古霉素耐药菌株,其对万古霉素和替考拉宁的MIC值为32.00 mg/L和64.00 mg/L,未检出vanA、vanB、vanC1、vanC2/3基因.148株MRCNS的SCCmec分型共有Ⅰ～Ⅴ5种型别,以Ⅲ型为主,Ⅳ型检出Ⅳa、Ⅳc、Ⅳd 3种亚型,并有较多的混合型存在.各基因型对多种抗生素呈不同程度的耐药.结论 安徽地区儿童MRCNS对多种常用抗生素不敏感,具有多重耐药性,有异质性万古霉素耐药菌株,应予警惕.不同类型的MRCNS所携带的SCCmec型别不同,SCCmecⅢ型为主要流行菌株.MRCNS对非β-内酰胺类抗生素耐药率的差异与SCCmec基因型别无明显相关性.%Objective To learn about the antibiotic resistance status of methicillin resistant coagulase negative staphylococcus(MRCNS),and to investigate the distribution and resistant feature of different staphylococcal chromosomal cassette mec(SCCmec) genotypes of children in Anhui,so as to guide clinical medication.Methods Resistance phenotype screening was conducted in coagulase negative staphylococcus,which were isolated from clinical strains in children in Anhui from 2010 to 2014 each year in September.MecA gene was detected by using PCR method in order to collect MRCNS.Minimal inhibitory concentrations (MIC) of 16 antibiotics were determined by adopting agar dilution method.Vacomycin-resistant strains were identified with population analysis and the Brain Heart Infusion vancomycin screen agar dilution method recommended by Clinical and Laboratory Standards Institute in 2013.Van gene and SCCmec types were detected by using PCR method.Results A total of 148 MRCNS strains were detected through the resistance phenotype screening and the detection of mecA gene.There were methicillin resistant staphylococcus epidermidis,methicillin resistant staphylococcus haemolyticus,methicillin resistant staphylococcus hominis,and other kinds of MRCNS,and the proportions of them were 44.59％ (66/148 cases),25.68％ (38/148 cases),19.59％ (29/148 cases) and 10.14％ (15/148 cases),respectively.The analysis of antibiotic resistance showed the antimicrobial resistant rates of MRCNS to Penicillin,Cefoperazone,Cefotaxime,Ceftriaxone,lmipenem and Meropenem were all 100％,to Erythromycin and Azithromycin,Ciprofloxacin,Clindamycin,Gentamicin,Lewofloxacin,Rifampincin,Chloramphenicol,Teicoplanin and Vancomycin were 92.57％,97.98％,83.78％,79.05％,43.24％,35.81％,24.32％,8.78％,2.03％ and 0.68％,respectively.There was 1 heterogeneous Vancomycin-resistant strain,which was resistant to both Vancomycin and Teicoplanin (with MIC 32.00 mg/L and 64.00 mg/L).No vanA,vanB,vanC1 or vanC2/3 gene was detected from heterogeneous Vancomycin-resistant strain by PCR.Ⅰ to Ⅴ SCCmec genotypes were detected from 148 MRCNS strains,and the major SCCmec type was SCCmec type Ⅲ,which was followed by hybrid type.Three subtypes of SCCmec type Ⅳ were identified,including Ⅳa,Ⅳc and Ⅳd.There were 148 MRCNS strains that showed different resistant phenotypes to various antibiotics.Conclusions The MRCNS strains of children in Anhui province showed multiple resistance to antibiotics.It should be on alert when heterogeneous Vaneomycin-resistant strain appeared.There were several different SCCmec types among several kinds of MRCNS,and SCCmec Ⅲ genotype was the major epidemic isolate.There was no significant correlation between the different resistance rates of non-β-lactamase antibiotics and SCCmec genotypes in MRCNS.
