Background and Objective Staphylococcus aureus is one of the major pathogens of nosocomial infections as wells as community-acquired (CA) infections worldwide. So far, large-scale comprehensive molecular and epidemiological characterisation of S. aureus from very diverse settings has not been carried out in India. The objective of this study is to evaluate the molecular, epidemiological and virulence characteristics of S. aureus in both community and hospital settings in Chennai, southern India. Methods S. aureus isolates were obtained from four different groups (a) healthy individuals from closed community settings, (b) inpatients from hospitals, (c) outpatients from hospitals, representing isolates of hospital-community interface and (d) HIV-infected patients to define isolates associated with the immunocompromised. Antibiotic susceptibility testing, multiplex polymerase chain reactions for detection of virulence and resistance determinants, molecular typing including Staphylococcal cassette chromosome mec (SCCmec) and agr typing, were carried out. Sequencing-based typing was done using spa and multilocus sequence typing (MLST) methods. Clonal complexes (CC) of hospital and CA methicillin-resistant S. aureus (MRSA) were identified and compared for virulence and resistance. Results and Conclusion A total of 769 isolates of S. aureus isolates were studied. The prevalence of MRSA was found to be 7.17%, 81.67%, 58.33% and 22.85% for groups a, b, c and d, respectively. Of the four SCCmec types (I, III, IV and V) detected, SCCmec V was found to be predominant. Panton-Valentine leucocidin toxin genes were detected among MRSA isolates harbouring SCCmec IV and V. A total of 78 spa types were detected, t657 being the most prevalent. 13 MLST types belonging to 9 CC were detected. CC1 (ST-772, ST-1) and CC8 (ST238, ST368 and ST1208) were found to be predominant among MRSA. CA-MRSA isolates with SCCmec IV and V were isolated from all study groups including hospitalised patients and were found to be similar by molecular tools. This shows that CA MRSA has probably infiltrated into the hospital settings.

中文翻译：

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耐甲氧西林金黄色葡萄球菌的克隆簇和毒力因子：社区获得性耐甲氧西林金黄色葡萄球菌渗透到印度南部钦奈医院环境的证据。

背景和目的 金黄色葡萄球菌是全世界医院感染和社区获得性（CA）感染的主要病原体之一。到目前为止，印度尚未对来自不同环境的金黄色葡萄球菌进行大规模全面的分子和流行病学表征。本研究的目的是评估印度南部钦奈社区和医院环境中金黄色葡萄球菌的分子、流行病学和毒力特征。方法 从四个不同组中获得金黄色葡萄球菌分离株（a）来自封闭社区环境的健康个体，（b）来自医院的住院患者，（c）来自医院的门诊患者，代表医院-社区界面的分离株，以及（d）HIV感染者定义与免疫功能低下相关的分离株。进行了抗生素敏感性测试、用于检测毒力和耐药性决定因素的多重聚合酶链反应、包括葡萄球菌盒式染色体 mec (SCCmec) 和 agr 分型在内的分子分型。基于测序的分型是使用 spa 和多位点序列分型 (MLST) 方法完成的。鉴定了医院和 CA 耐甲氧西林金黄色葡萄球菌 (MRSA) 的克隆复合物 (CC)，并比较了毒力和耐药性。结果和结论 总共研究了 769 个金黄色葡萄球菌分离株。a、b、c、d 组 MRSA 患病率分别为 7.17%、81.67%、58.33% 和 22.85%。在检测到的四种 SCCmec 类型（I、III、IV 和 V）中，发现 SCCmec V 占主导地位。在含有 SCCmec IV 和 V 的 MRSA 分离株中检测到 Panton-Valentine leuucocidin 毒素基因。总共检测到 78 种 spa 类型，其中 t657 是最常见的。检测到属于 9 个 CC 的 13 个 MLST 类型。发现 CC1（ST-772、ST-1）和 CC8（ST238、ST368 和 ST1208）在 MRSA 中占主导地位。具有 SCCmec IV 和 V 的 CA-MRSA 分离株从包括住院患者在内的所有研究组中分离出来，并通过分子工具发现相似。这表明 CA MRSA 可能已经渗透到医院环境中。