146例金黄色葡萄球菌中红霉素对克林霉素诱导耐药分析

目的了解金黄色葡萄球菌(SA)对红霉素和克林霉素的耐药性,检测红霉素对克林霉素诱导耐药的发生率及诱导耐药基因。方法采用美国临床实验室标准化协会(CLSI)推荐的纸片扩散法,用头孢西丁纸片检测耐甲氧西林金黄色葡萄球菌(MRSA)并以红霉素、克林霉素双纸片法(D试验)分析红霉素对克林霉素诱导耐药表型,用聚合酶链反应(PCR)检测耐药基因。结果 146株SA中MRSA占57.5%。SA对红霉素及克林霉素同时耐药的有82株,占56.2%,红霉素耐药而克林霉素敏感或中介的有34株,其中D试验阳性26株,红霉素诱导克林霉素耐药率76.5%。红霉素耐药而克林霉素敏感或中介的MRSA和甲氧西林敏感金黄色葡萄球菌(MSSA)中D试验阳性分别为80.0%和71.4%。克林霉素耐药菌株主要由erm基因决定,结构型耐药菌株主要耐药基因为ermA,诱导型耐药菌株的主要耐药基因为ermC。结论临床微生物实验室应加强对SA中克林霉素诱导耐药的检测,以指导临床医师合理选用大环内酯类、林可酰胺类抗菌药物。

Analysis of clindamycin-induced resistance by erythromycin among 146 strains of Staphylococcus aureus

Objective To investigate the resistance of Staphylococcus aureus（SA） to erythromycin and clindamycin,and to detect the incidence of clindamycin-induced resistance by erythromycin and the induction of resistance genes.Methods The disk diffusion method recommended by the standards of Clinical and Laboratory Standards Institute（CLSI） was used,and cefoxitin disk diffusion test was used for the detection of meticillin-resistant Staphylococcus aureus（MRSA）.The inducible resistance phenotype of erythromycin to clindamycin was analyzed by clindamycin and erythromycin double-disk diffusion method（D test）,and the resistant gene was detected by polymerase chain reaction（PCR）.Results In 146 strains of SA,MRSA accounted for 57.5%.SA resistant to both erythromycin and clindamycin were 82 strains,accounted for 56.2%.The erythromycin resistant and clindamycin susceptible or intermediate strains were 34 strains,which D test positive were 26 strains,the percentage for inducible resistance of erythromycin to clindamycin was 76.5%.The positive rates of D test were 80.0% and 71.4% in erythromycin resistant and clindamycin susceptible or intermediate MRSA and methicillin-sensitive Staphylococcus aureus（MSSA）.The predominant gene for clindamycin resistance was erm.The predominant gene for constitutive resistance to clindamycin was ermA.The predominant gene for inducible resistance to clindamycin was ermC.Conclusions The detection of inducible clindamycin resistance in SA should be paid attention in clinical microbiology laboratories in order to guide physicians to select antimicrobial agents correctly such as macrolides and lincosamides.