Sanyal D, Greenwood D
Department of Microbiology, University Hospital, Queen's Medical Centre, Nottingham.
J Med Microbiol. 1993 Sep;39(3):204-10. doi: 10.1099/00222615-39-3-204.
Ultra-thin section transmission electronmicroscopy revealed that two of three glycopeptide-resistant strains of Staphylococcus epidermidis had abnormally thick cell walls, a finding consistent with the view that the reduction in susceptibility may result from the overproduction of glycopeptide binding sites within the cell-wall peptidoglycan. The third resistant strain had a slightly thickened cell wall with an irregular, roughened outline; this strain also underwent autolysis on prolonged incubation on blood agar and the resistance may be associated with abnormal cell-wall synthesis. Sub-MIC concentrations of vancomycin and teicoplanin caused surface damage to a proportion of cocci able to grow in the presence of antibiotic. Exposure to teicoplanin was additionally associated with the formation of filamentous forms and variable amounts of extracellular material. Transmission electronmicroscopy showed that both antibiotics exerted effects within the bacterial cytoplasm of the resistant strains that were not seen in an NCTC control strain: intracellular lamellae and structures resembling mesosomes were observed in the former. These effects were more noticeable in cocci exposed to vancomycin. Bacteria exposed to teicoplanin often showed abnormal septation and, in some preparations, a double-layered cell wall.
超薄切片透射电子显微镜检查显示，三株耐糖肽表皮葡萄球菌中有两株细胞壁异常增厚，这一发现与以下观点一致，即敏感性降低可能是由于细胞壁肽聚糖内糖肽结合位点的过度产生所致。第三株耐药菌株的细胞壁略有增厚，轮廓不规则且粗糙；该菌株在血琼脂上长时间培养后也会发生自溶，其耐药性可能与异常的细胞壁合成有关。低于最低抑菌浓度的万古霉素和替考拉宁会对一部分能够在抗生素存在下生长的球菌造成表面损伤。接触替考拉宁还会导致丝状形态的形成以及不同数量的细胞外物质。透射电子显微镜检查表明，这两种抗生素在耐药菌株的细菌细胞质内产生了在NCTC对照菌株中未观察到的效应：在前者中观察到了细胞内片层和类似中间体的结构。这些效应在接触万古霉素的球菌中更为明显。接触替考拉宁的细菌经常表现出异常的分隔，并且在一些标本中呈现出双层细胞壁。
