Staphylococcus epidermidis is a common cause of biomedical device-associated infections. Agr is the major quorum sensing system in staphylococci and regulates virulence factors. Four agr-specificity groups exist in S. epidermidis, and chronic S. epidermidis infections are hypothesised to select for agr-negative phenotypes. Therefore, we investigated S. epidermidis strains from prosthetic joint- and catheter-associated infections to establish i) whether an infection selects for an agr-negative phenotype; ii) the importance of PSMγ and iii) if the agr-specificity group is infection dependent. S. epidermidis nasal isolates from healthy volunteers were used as controls. The distribution of agr-specificity groups was significantly different between infection and control episodes, but did not distinguish between the infection types. PSMγ secretion was used to determine agr-activity and HPLC analysis showed that 44% of prosthetic and 32% of catheter-associated episodes produced no PSMγ in comparison to 8% of the control strains. However, PSMγ expression did not always correlate with RNAIII up-regulation, indicating that PSMγ synthesis is likely influenced by additional post-transcriptional control. The data suggests chronic S. epidermidis infections favour agr-specificity group 1 but the results suggest that they do not select for an agr-negative phenotype. Further studies are required to explore the mechanisms underlying the selection and survival of these S. epidermidis phenotypes isolated from biomedical device-associated infections.

中文翻译：

---

使用PSMγ，agr，RNAIII和生物膜形成作为生物标记物来定义来自慢性生物医学装置相关感染的侵入性表皮葡萄球菌的局限性。

表皮葡萄球菌是生物医学设备相关感染的常见原因。Agr是葡萄球菌中主要的群体感应系统，可调节毒力因子。表皮葡萄球菌中存在四个agr特异性组，并假设慢性表皮葡萄球菌感染可以选择agr阴性表型。因此，我们研究了来自假体关节和导管相关感染的表皮葡萄球菌菌株，以确定：i）感染是否选择了农业阴性表型；ii）PSMγ的重要性，以及iii）如果agr特异性组是感染依赖性的。来自健康志愿者的表皮葡萄球菌鼻分离物用作对照。在感染和对照发作之间，农艺特异性组的分布有显着差异，但没有区分感染类型。PSMγ分泌用于确定农业活动性，HPLC分析表明，与8％的对照菌株相比，44％的假体和32％的导管相关发作不产生PSMγ。但是，PSMγ的表达并不总是与RNAIII的上调相关，这表明PSMγ的合成很可能受到其他转录后控制的影响。数据表明，慢性表皮葡萄球菌感染有利于农业特异性群1，但结果表明，他们没有选择农业阴性表型。需要进一步的研究来探索从生物医学设备相关感染中分离出的这些表皮葡萄球菌表型的选择和存活的潜在机制。