金葡菌细胞壁变化与对万古霉素耐药的关系

目的了解金葡菌细胞壁变化与万古霉素耐药的关系，探讨耐药机制。方法将1株从临床标本中分离的异质性耐万古霉素的金葡菌（h-VRSA）在含有不同浓度的万古霉素培养基上连续诱导转种，用微量肉汤稀释法和菌谱分析法检测其对万古霉素的敏感性；同时采用扫描电镜和透射电镜分别对细胞壁的表面结构和厚度进行摄片观察；用PCR方法检测万古霉素耐药基因（vanA、vanB和vanC）。结果随万古霉素诱导浓度的增加，金葡菌对万古霉素的MIC逐渐增加；菌谱分析显示耐药亚群逐渐增加；电镜摄片可见细胞壁增厚，细胞壁粗糙，有结节状凸起；van基因检测为阴性。结论在万古霉素的选择性压力下金葡菌的耐药性可逐渐增加，细胞壁增厚是金葡菌对万古霉素耐药的重要机制。

The relationship between the thickening of cell wall and vancomycin resistance of Staphylococcus aureus

Objective To investinggate the relationship between the thickening of cell wall and the susceptibility of vancomycin in S.aureus and study the resistant mechanism. Methods A heterogeneous vancomycin-resistant Staphylococcus aureus (h-VRSA) isolated from clinical specimen was inoculated on the agar plate with the increasing concentration of vancomycin. The susceptibility to vancomycin was assessed by the broth dilution method and population analysis profiles. The cell surface structure and cell-wall thickness were observed by scan electron microscopy and transmission electron microscopy, respectively. The vancomycin resistance genes were detected by polymerase chain reaction. Results The MIC and the resistance population of S. aureus to vancomycin were increased. The cell wall was incrassated and the surface was rough and nodal. The vancomycin resistance genes were not detected. Conclusion Under vancomycin selective pressure, the resistance to vancomycin of S. aureus could be increased. The thickening of cell wall is one of the important resistant mechanism.