Tenover F C, Lancaster M V, Hill B C, Steward C D, Stocker S A, Hancock G A, O'Hara C M, McAllister S K, Clark N C, Hiramatsu K
Hospital Infections Program, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
J Clin Microbiol. 1998 Apr;36(4):1020-7. doi: 10.1128/JCM.36.4.1020-1027.1998.
During the last several years a series of staphylococcal isolates that demonstrated reduced susceptibility to vancomycin or other glycopeptides have been reported. We selected 12 isolates of staphylococci for which the vancomycin MICs were > or =4 microg/ml or for which the teicoplanin MICs were > or =8 microg/ml and 24 control strains for which the vancomycin MICs were < or =2 microg/ml or for which the teicoplanin MICs were < or =4 microg/ml to determine the ability of commercial susceptibility testing procedures and vancomycin agar screening methods to detect isolates with reduced glycopeptide susceptibility. By PCR analysis, none of the isolates with decreased glycopeptide susceptibility contained known vancomycin resistance genes. Broth microdilution tests held a full 24 h were best at detecting strains with reduced glycopeptide susceptibility. Disk diffusion did not differentiate the strains inhibited by 8 microg of vancomycin per ml from more susceptible isolates. Most of the isolates with reduced glycopeptide susceptibility were recognized by MicroScan conventional panels and Etest vancomycin strips. Sensititre panels read visually were more variable, although with some of the panels MICs of 8 microg/ml were noted for these isolates. Vitek results were 4 microg/ml for all strains for which the vancomycin MICs were > or =4 microg/ml. Vancomycin MICs on Rapid MicroScan panels were not predictive, giving MICs of either < or =2 or > or =16 microg/ml for these isolates. Commercial brain heart infusion vancomycin agar screening plates containing 6 microg of vancomycin per ml consistently differentiated those strains inhibited by 8 microg/ml from more susceptible strains. Vancomycin-containing media prepared in-house showed occasional growth of susceptible strains, Staphylococcus aureus ATCC 29213, and on occasion, Enterococcus faecalis ATCC 29212. Thus, strains of staphylococci with reduced susceptibility to glycopeptides, such as vancomycin, are best detected in the laboratory by nonautomated quantitative tests incubated for a full 24 h. Furthermore, it appears that commercial vancomycin agar screening plates can be used to detect these isolates.
在过去几年里，已有一系列对万古霉素或其他糖肽类药物敏感性降低的葡萄球菌分离株的报道。我们选择了12株万古霉素MIC≥4μg/ml或替考拉宁MIC≥8μg/ml的葡萄球菌分离株，以及24株万古霉素MIC≤2μg/ml或替考拉宁MIC≤4μg/ml的对照菌株，以确定商业药敏试验程序和万古霉素琼脂筛选方法检测糖肽类药物敏感性降低的分离株的能力。通过PCR分析，糖肽类药物敏感性降低的分离株均未含有已知的万古霉素耐药基因。进行24小时的肉汤微量稀释试验在检测糖肽类药物敏感性降低的菌株方面效果最佳。纸片扩散法无法区分每毫升8μg万古霉素抑制的菌株与更敏感的分离株。大多数糖肽类药物敏感性降低的分离株可被MicroScan常规鉴定板和Etest万古霉素试纸条识别。目视读取的Sensititre鉴定板变异性更大，不过其中一些鉴定板对这些分离株记录的MIC为8μg/ml。对于万古霉素MIC≥4μg/ml的所有菌株，Vitek检测结果均为4μg/ml。Rapid MicroScan鉴定板上的万古霉素MIC无法预测，这些分离株的MIC要么≤2μg/ml，要么≥16μg/ml。每毫升含6μg万古霉素的商业脑心浸液万古霉素琼脂筛选平板能够持续区分每毫升8μg万古霉素抑制的菌株与更敏感的菌株。自制的含万古霉素培养基偶尔会出现敏感菌株金黄色葡萄球菌ATCC 29213的生长，偶尔也会出现粪肠球菌ATCC 29212的生长。因此，在实验室中，通过非自动化的定量试验并孵育24小时，能最好地检测出对糖肽类药物（如万古霉素）敏感性降低的葡萄球菌菌株。此外，商业万古霉素琼脂筛选平板似乎可用于检测这些分离株。
