Domaracki B E, Evans A, Preston K E, Fraimow H, Venezia R A
Department of Pathology and Laboratory Medicine, Albany Medical Center, New York 12208, USA.
Eur J Clin Microbiol Infect Dis. 1998 Mar;17(3):143-50. doi: 10.1007/BF01691109.
Vancomycin resistance in methicillin-resistant staphylococci presents a potential therapeutic problem. In order to understand the impact of low-level vancomycin resistance in coagulase-negative staphylococci, stepwise selection of vancomycin resistance was accomplished by growing Staphylococcus haemolyticus in culture media with increasing concentrations of vancomycin. A >40-fold increase in susceptibility to beta-lactam antibiotics was observed. No obvious alterations in the growth curve, the presence of the mecA gene, total DNA restriction fragment length polymorphism (RFLP), beta-lactamase production, or the crude protein fraction were detected in the Staphylococcus haemolyticus-derived clones when compared to the original isolate. The proportion of the oxacillin-heteroresistant population also remained similar. A comparable phenomenon occurred with the selection of Staphylococcus epidermidis exhibiting low-level resistance to vancomycin. Additionally, it was observed that clinical isolates of coagulase-negative staphylococci grown in the presence of sub-minimum inhibitory concentrations of either vancomycin or teicoplanin lost their high-level resistance to oxacillin. Checkerboard tests showed that the combination of vancomycin and oxacillin was synergistic for two isolates of Staphylococcus haemolyticus, two of four isolates of Staphylococcus epidermidis, and one isolate of Staphylococcus hominis.
耐甲氧西林葡萄球菌中的万古霉素耐药性带来了一个潜在的治疗问题。为了了解凝固酶阴性葡萄球菌中低水平万古霉素耐药性的影响，通过在含有浓度递增的万古霉素的培养基中培养溶血葡萄球菌来逐步筛选万古霉素耐药性。观察到对β-内酰胺类抗生素的敏感性增加了40倍以上。与原始分离株相比，在溶血葡萄球菌衍生的克隆中未检测到生长曲线、mecA基因的存在、总DNA限制性片段长度多态性（RFLP）、β-内酰胺酶产生或粗蛋白组分有明显改变。对苯唑西林异质性群体的比例也保持相似。在筛选出对万古霉素表现出低水平耐药性的表皮葡萄球菌时也出现了类似现象。此外，观察到在亚最低抑菌浓度的万古霉素或替考拉宁存在下生长的凝固酶阴性葡萄球菌临床分离株失去了对苯唑西林的高水平耐药性。棋盘法试验表明，万古霉素和苯唑西林的组合对两株溶血葡萄球菌、四株表皮葡萄球菌中的两株以及一株人葡萄球菌具有协同作用。
