Reduced susceptibility of Staphylococcus aureus to vancomycin and platelet microbicidal protein correlates with defective autolysis and loss of accessory gene regulator (agr) function
Reduced susceptibility of Staphylococcus aureus to vancomycin and platelet microbicidal protein correlates with defective autolysis and loss of accessory gene regulator (agr) function
复制标题
DOI：
10.1128/aac.49.7.2687-2692.2005
复制
发表时间：
2005-07-01
影响因子：
4.9
通讯作者：
Bayer, AS
中科院分区：
文献类型：
--
作者：
Sakoulas, G;Eliopouios, GM;Bayer, AS
Agr功能丧失、万古霉素暴露和异常自溶都与GISA表型的发展和体外对凝血酶诱导的血小板杀菌蛋白(TPMPs)的低水平耐药性有关。我们在体外检测了这些参数之间的潜在相互关系，这些参数具有良好的特征，实验室衍生的等基因和临床分离的金黄色葡萄球菌。实验室分离的金黄色葡萄球菌包括RN6607(Agrii阳性亲本)和RN6607V(万古霉素传代变种；异源GISA)，RN9120(RN6607 agr：：ted M，agr II基因敲除亲本)，RN9120V(万古霉素传代变种)和RN9120-GISA(万古霉素传代，GISA)。来自一名顽固性耐甲氧西林金黄色葡萄球菌(MRSA)心内膜炎患者的两个系列分离株也被研究：A5937(Agrii阳性初始分离株)和A5940(Agrii缺陷/异种GISA分离株，在长期应用万古霉素后获得)。用分光光度法检测Triton X-100和万古霉素诱导的裂解谱，检测菌株暴露于1或2微克/毫升后对TPMP的敏感性。对于Agrii完整菌株RN6607，体外万古霉素暴露与万古霉素MIC的适度增加和TPMP的杀伤力降低有关，但裂解谱没有变化。相反，在Agrii阴性的RN9120中，万古霉素暴露产生了异源GISA表型，并与裂解缺陷和TPMP体外杀伤减少有关。在临床分离株中，在延长万古霉素治疗期间，Agrii功能丧失伴随着异源GISA表型的出现和TPMP杀伤的减少，而裂解谱没有显著变化。在体外或体内万古霉素暴露期间，Agrii功能的丧失与异型GISA表型的出现之间存在关联。在体外，这些事件与有缺陷的溶解和降低对TPMP的易感性有关。这些发现背后的确切机制(S)是目前调查的主题。
Loss of agr function, vancomycin exposure, and abnormal autolysis have been linked with both development of the GISA phenotype and low-level resistance in vitro to thrombin-induced platelet microbicidal proteins (tPMPs). We examined the potential in vitro interrelationships among these parameters in well-characterized, isogenic laboratory-derived and clinical Staphylococcus aureus isolates. The laboratory-derived S. aureus strains included RN6607 (agrII-positive parent) and RN6607V (vancomycin-passaged variant; hetero-GISA), RN9120 (RN6607 agr::tetM, agr II knockout parent), RN9120V (vancomycin-passaged variant), and RN9120-GISA (vancomycin passaged, GISA). Two serial isolates from a vancomycin-treated patient with recalcitrant, methicillin-resistant S. aureus (MRSA) endocarditis were also studied: A5937 (agrII-positive initial isolate) and A5940 (agrII-defective/hetero-GISA isolate obtained after prolonged vancomycin administration). In vitro tPMP susceptibility phenotypes were assessed after exposure of strains to either 1 or 2 mu g/ml. Triton X-100- and vancomycin-induced lysis profiles were determined spectrophotometrically. For agrII-intact strain RN6607, vancomycin exposure in vitro was associated with modest increases in vancomycin MICs and reduced killing by tPMP, but no change in lysis profiles. In contrast, vancomycin exposure of agrII-negative RN9120 yielded a hetero-GISA phenotype and was associated with defects in lysis and reduced in vitro killing by tPMP. In the clinical isolates, loss of agrII function during prolonged vancomycin therapy was accompanied by emergence of the hetero-GISA phenotype and reduced tPMP killing, with no significant change in lysis profiles. An association was identified between loss of agrII function and the emergence of hetero-GISA phenotype during either in vitro or in vivo vancomycin exposure. In vitro, these events were associated with defective lysis and reduced susceptibility to tPMP. The precise mechanism(s) underlying these findings is the subject of current investigations.