Abimannan Nagarajan, Sumathi G, Krishnarajasekhar O R, Sinha Bhanu, Krishnan Padma
Department of Microbiology, University of Madras, Chennai; Department of Microbiology, Food Analysis Laboratory, Tamil Nadu Food Safety and Drugs Administration, Madurai, Tamil Nadu, India.
Institute of Microbiology, Rajiv Gandhi Government General Hospital, Chennai, Tamil Nadu, India.
Indian J Med Microbiol. 2019 Jul-Sep;37(3):326-336. doi: 10.4103/ijmm.IJMM_18_271.
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.
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.
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.
金黄色葡萄球菌是全球医院感染以及社区获得性（CA）感染的主要病原体之一。到目前为止，印度尚未对来自非常多样化环境的金黄色葡萄球菌进行大规模的综合分子和流行病学特征分析。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。
从四个不同组获得金黄色葡萄球菌分离株：（a）封闭社区环境中的健康个体，（b）医院住院患者，（c）医院门诊患者，代表医院 - 社区界面的分离株，以及（d）HIV感染患者以确定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。基于测序的分型使用spa和多位点序列分型（MLST）方法进行。鉴定了医院和社区获得性耐甲氧西林金黄色葡萄球菌（MRSA）的克隆复合体（CC），并比较了其毒力和耐药性。
共研究了769株金黄色葡萄球菌分离株。发现a、b、c和d组的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，SCCmec V最为常见。在携带SCCmec IV和V的MRSA分离株中检测到杀白细胞素毒素基因。共检测到78种spa类型，t657最为常见。检测到属于9个CC的13种MLST类型。CC1（ST - 772，ST - 1）和CC8（ST238，ST368和ST1208）在MRSA中占主导地位。带有SCCmec IV和V的社区获得性MRSA分离株从包括住院患者在内的所有研究组中分离得到，并且通过分子工具发现它们相似。这表明社区获得性MRSA可能已经渗透到医院环境中。
