万古霉素异质性耐药葡萄球菌的分离及其药物敏感性分析

Isolation of heterogeneously resistant Staphylococci to vancomycin and its susceptibility to common antibiotics

目的 调查葡萄球菌对万古霉素异质性耐药亚群发生频率以及对常见抗生素的药物敏感性。方法 利用菌群分析法筛选万古霉素异质性耐药葡萄球菌亚群 ,Microscan Microbiology System对萄萄球菌分型和鉴定并分析对 19种常用抗生素的药物敏感性。结果 115株耐甲氧西林的葡萄球菌 ,9株对万古霉素耐药亚群的 MIC8～ 12 mg/ L,其发生频率为 10 - 4～ 10 - 7,其中 3株金葡球菌 ,6株溶血性葡萄球菌。传至 7代后万古霉素 MIC6 4 mg/ L。对 19种抗生素药敏显示 ,万古霉素敏感 2株、中介 7株 ,敏感率 2 2 .2 % ;利福平敏感7株 (MIC≤ 1mg/ L)、中介 1株 (MIC=2 mg/ L)及耐药 1株 (MIC>2 mg/ L)、敏感率 77.8% ;SMZ/ TMP敏感 6株 (MIC≤ 2 / 38mg/ L)、耐药 3株 (MIC>2 / 38mg/ L) ,敏感率 6 6 .7% ;克林霉素敏感 3株 (MIC=0 .5或≤ 0 .2 5 )、耐药 6株 (MIC>2 mg/ L) ,敏感率 33.3% ;四环素敏感 3株 (MIC≤ 2 mg/ L)、耐药 6株 (MIC>8mg/L) ,敏感率 33.3% ;左氧氟沙星敏感 1株 (MIC≤ 2 mg/ L)、耐药 8株 (MIC>4 mg/ L) ,敏感率 11.1%。其余 13种抗生素耐药。结论 下呼吸道分离的葡萄球菌存在一定频率的对万古霉素异质性耐药株 ,可能是万古霉素治疗失败的原因之一 ,利福平、SMZ/ TMP具有较好的敏感性 。

Objective To investigate the frequency of heterogeneously resistant Staphylococci to vanco mycin and its susceptibility to common antibiotics. Methods Resistant subpopulation of Staphylococci to vancomycin were screened by population analysis method and identified and classified by the Microscan Microbiology System.The susceptibility of heterogeneously resistant Staphylococci to vancomycin and to other common antibiotics were detected by the Microscan Microbiology System. Results Of 115 strains of methicillin resistant Staphylococci, 9 strains (including 3 strains of Staphylococcus aureus and 6 strains of Staphylococcus haemolyticus) emerged heterogeneously resistant to vancomycin with MIC of 8 to 12mg/L and frequency of 10 -4 to 10 -7 and the 7 th subcultures with MIC of 64mg/L. The results of drug suscentipility showed that the sensitive rate of 9 hetero VRS to 19 kinds of antibiotics was as follows: Vancomycin 22.2% (2 sensitive, 7 intermediate), rifampin 77.8% [7 sensitive (MIC≤1mg/L), 1 intermediate (MIC=2mg/L), 1 resistamt (MIC>2mg/L)], SMZ/TMP 66.7% [6 sensitive (MIC≤2/38mg/L), 3 resistant (MIC>2/38mg/L)], Clindamycin 33.3% [3 sensitive (MIC=0.5 or ≤0.25mg/L), 6 resistant (MIC>2mg/L)], tetracycline 33.3% [3 sensitive (MIC≤2mg/L), 6 resistant (MIC>8mg/L)], levofloxacin 11.1% [1 sensitive (MIC≤2mg/L), 8 resistant (MIC≥4mg/L)]. Other 13 antibiotics were resistant to 9 stains of Staphylococci. Conclusions There were some strains heterogeneously resistance to vancomycan Staphylococci isolated from lower respiratory tract and these bacteria may play an important role in therapeutic failure of vancomycin. Rifampin and SMZ/TMP had potent antimicrobial activities against them followed by clindamycin and tetracycline. These antibiotics may be considered in treating Staphylococci reduced susceptibility to vancomycin.