溶血葡萄球菌庆大霉素耐药表型与基因型分析

目的研究溶血葡萄球菌庆大霉素耐药表型与基因型。方法用琼脂稀释法测定63株溶血葡萄球菌对苯唑西林、庆大霉素和其他5种抗生素的最低抑菌浓度（MIC），用聚合酶链反应（PCR）检测mecA和aac（6’）．aph（2”）耐药基因。结果63株溶血葡萄球菌对庆大霉素的耐药率为74．6％，MIC50、MIC90分别为64和128μg／mL.庆大霉素不敏感的甲氧西林耐药溶血葡萄球菌（MRSH）对环丙沙星和红霉素的耐药率（85．7％和87．8％）远高于庆大霉素敏感的MRSH（0．0％和46．2％，P〈0．005）。13株庆大霉素敏感的溶血葡萄球菌扩增aac（6’）＋aph（2”）基因均阴性，50株庆大霉素不敏感的溶血葡萄球菌（MIC为8～≥128μg／mL）均携带aac（6’）-aph（2”）基因，其中49株同时携带mecA基因。结论aac（6’）-aph（2”）基因是溶血葡萄球菌对庆大霉素产生耐药的主要机制。

Investigaton of gentamycin resistance genotype and phenotype in Staphylococcus haemolyticus

Objective To investigate the gentamycin resistance genotype and phenotype among the clinical isolates of Staphylococcus haemolyticus （ S. haemolyticus ）. Methods Agar dilution method was performed to detect the minimal inhibition concentrations （MIC） of oxacillin, gentamycin and other five antimicrobial agents against 63 strains of S. haemolyticus, and the resistance genes of mecA and aac （6＇）-aph （2”） were investigated by polymerase chain reaction （PCR） in all clinical isolates. Results 74.6% of isolates were resistant to gentamycin, with the MIC50 of 64 μg/mL and MIC90 of 128 μg/mL. Methicillin-resistant S. haemolyticus （MRSH） non-susceptible to gentamycin showed higher resistance rates to cipfloxacin and erythromycin than gentamycin -susceptible MRSH （85.7% and 87.8% vs 0% and 46.2 %, respectively, P 〈 0. 005 ）. 13 gentamycin-susceptible isolates were not found having aac （ 6＇ ） -aph （2”） gene, while this gene was detected in 50 isolates non-susceptible to gentamycin （ MIC 8-≥ 128 μg/mL）, and 49 strains among them carried also mecA gene. Conclusions aac（6＇）-aph（2”） gene plays a major part in S. haemolyticus resistant to gentamycin.