Gerberding J L, Miick C, Liu H H, Chambers H F
Department of Medicine, University of California, San Francisco 94110.
Antimicrob Agents Chemother. 1991 Dec;35(12):2574-9. doi: 10.1128/AAC.35.12.2574.
Six selected strains of Staphylococcus aureus classified as borderline oxacillin-resistant, according to standard disk diffusion and microdilution susceptibility test methods, and seven methicillin-resistant and seven methicillin-susceptible control strains were examined for the presence of penicillin-binding protein 2a (PBP 2a) by fluorography and immunoblotting and for DNA hybridization with a mec-specific probe in a dot blot assay. Oxacillin agar screen tests with and without NaCl supplementation were also performed with all strains. PBP 2a was detected both by fluorography and by immunoblotting in all seven methicillin-resistant control strains and in none of the susceptible controls. PBP 2a was detected in two borderline strains. Results of agar screen tests performed without NaCl supplementation were completely concordant with susceptibility determined by PBP 2a and mec detection methods. Agar screening with NaCl supplementation was less accurate. These findings were confirmed with 20 additional borderline strains. Direct detection methods for the presence of PBP 2a or mec, the gene encoding it, allow accurate and definitive classification of borderline strains. Further efforts to develop a rapid, clinically useful, antibody detection system for PBP 2a are warranted.
根据标准纸片扩散法和微量稀释药敏试验方法，选取6株被归类为对苯唑西林耐药临界的金黄色葡萄球菌菌株，并对7株耐甲氧西林和7株甲氧西林敏感的对照菌株进行了研究，通过荧光显影和免疫印迹法检测青霉素结合蛋白2a（PBP 2a）的存在情况，并在斑点印迹试验中用mec特异性探针进行DNA杂交。所有菌株还进行了添加和不添加氯化钠的苯唑西林琼脂筛选试验。在所有7株耐甲氧西林对照菌株中，通过荧光显影和免疫印迹法均检测到了PBP 2a，而在敏感对照菌株中均未检测到。在2株临界菌株中检测到了PBP 2a。不添加氯化钠进行的琼脂筛选试验结果与通过PBP 2a和mec检测方法确定的药敏性完全一致。添加氯化钠的琼脂筛选准确性较低。另外20株临界菌株也证实了这些发现。对PBP 2a或其编码基因mec的直接检测方法可对临界菌株进行准确和明确的分类。有必要进一步努力开发一种快速、临床实用的PBP 2a抗体检测系统。
