Bakthavatchalam Yamuna Devi, Triplicane Dwarakanathan Hariharan, Munusamy Elakkiya, Jennifer Lydia, Veeraraghavan Balaji
1 Department of Clinical Microbiology, Christian Medical College, Vellore, India.
2 Department of Orthopaedics, Christian Medical College, Vellore, India.
Microb Drug Resist. 2019 Apr;25(3):413-420. doi: 10.1089/mdr.2018.0292. Epub 2019 Feb 14.
Staphylococcal surface protein sasX is a colonization mediating virulence factor in ST239 methicillin-resistant Staphylococcus aureus (MRSA) strains, which potentially contribute to its successful establishment. We aimed to study the presence and dissemination of sasX in clinical MRSA isolates and among MRSA carriers. A total of 450 nonduplicate clinical MRSA isolates recovered from blood cultures between 2013 and 2017 were included in this study. In addition, 93 nasal swabs were collected from patients receiving hemodialysis, after obtaining consent and screening for MRSA colonization. sasX polymerase chain reaction and sequencing were carried out for all isolates. Multilocus sequence typing was performed for all sasX-positive isolates. Of the tested clinical MRSA isolates, 11% (n = 48) were positive for sasX gene. Among hemodialysis patients, 26% (n = 24) were characterized as MRSA carriers. However, all MRSA strains isolated from nasal swab were negative for sasX gene. Overall, we observed 10% (11% in clinical MRSA isolates and 0% in MRSA carriers) of sasX-positive MRSA in this study. ST239 and ST368 were the predominant sasX carrying MRSA lineages. The majority of sasX carrying MRSA strains were characterized as Staphylococcus epidermidis surface protein I (sesI; 71%), a sasX homolog native to S. epidermidis. This study highlights the dissemination of sasX/sesI to ST368 (CC8), ST3324 (CC8), ST772 (CC1), and ST22 (CC22). The presence of S. epidermidis-specific invasive factor sesI in clinical MRSA strains provides evidence for horizontal transfer between these closely related species.
葡萄球菌表面蛋白sasX是ST239耐甲氧西林金黄色葡萄球菌（MRSA）菌株中的一种介导定植的毒力因子，这可能有助于其成功定植。我们旨在研究sasX在临床MRSA分离株及MRSA携带者中的存在情况和传播情况。本研究纳入了2013年至2017年间从血培养中分离出的450株非重复临床MRSA分离株。此外，在获得同意并筛查MRSA定植后，从接受血液透析的患者中采集了93份鼻拭子。对所有分离株进行了sasX聚合酶链反应和测序。对所有sasX阳性分离株进行多位点序列分型。在检测的临床MRSA分离株中，11%（n = 48）的sasX基因呈阳性。在血液透析患者中，26%（n = 24）被鉴定为MRSA携带者。然而，从鼻拭子中分离出的所有MRSA菌株的sasX基因均为阴性。总体而言，在本研究中我们观察到10%（临床MRSA分离株中为11%，MRSA携带者中为0%）的sasX阳性MRSA。ST239和ST368是携带sasX的主要MRSA谱系。大多数携带sasX的MRSA菌株被鉴定为表皮葡萄球菌表面蛋白I（sesI；71%），这是表皮葡萄球菌特有的sasX同源物。本研究强调了sasX/sesI向ST368（CC8）、ST3324（CC8）、ST772（CC1）和ST22（CC22）的传播。临床MRSA菌株中存在表皮葡萄球菌特异性侵袭因子sesI为这些密切相关物种之间的水平转移提供了证据。
