Centre for Healthcare-Associated Infections, Antimicrobial Resistance and Mycoses, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa.
Faculty of Health Sciences, Department of Clinical Microbiology and Infectious Diseases, School of Pathology, University of Witwatersrand, Johannesburg, South Africa.
PLoS One. 2021 Jun 29;16(6):e0253883. doi: 10.1371/journal.pone.0253883. eCollection 2021.
Methicillin-resistant Staphylococcus aureus (MRSA) is a highly clonal pathogen causing infections in various settings. The aim of this study was to determine if healthcare-associated (HA) MRSA isolates with the same spa-type originating from two geographically distinct hospitals in South Africa were genetically related based on PFGE. Furthermore, a small subset of MRSA isolates were characterised with WGS and then compared to PFGE to determine if PFGE is still a reliable method to define outbreaks and/or transmission chains.
Staphylococcus aureus isolated from blood cultures (BC) were submitted to the Centre for Healthcare-Associated Infections, Antimicrobial Resistance and Mycoses (CHARM) as part of a laboratory-based surveillance programme (GERMS-SA). The identified HA-MRSA isolates underwent molecular characterisation [Staphylococcal Chromosome Cassette (SCC) mec and spa-typing]. Pulsed-field gel electrophoresis (PFGE) was performed on selected isolates with the same spa-type. Twenty-one MRSA isolates were selected for whole-genome sequencing (WGS) based on spa-type, PFGE clustering, time and place of isolation.
Eighteen percent (n = 95/529) and 33% (n = 234/710) of isolates collected, from two public tertiary academic hospitals in the Gauteng (GAU) and the Western Cape (WC) provinces, were identified as MRSA, respectively. The most dominant clone in the GAU hospital was t037-III-MRSA (43.2%; n = 41/95). The most dominant clones in the WC hospital was t037-III-MRSA (23.9%, n = 56/234) and t045-I-MRSA (23.5%, n = 55/234). The GAU-t037-III-MRSA cases and WC-t045-I-MRSA cases occurred in the paediatric patient population, whereas the WC-t037-III-MRSA cases occurred in the adult patient population. A novel spa-type (t19935) was detected in the GAU hospital. PFGE showed that the GAU- and WC-t037-III-MRSA isolates were genetically indistinguishable, as well as most of the WC-t045-I-MRSA isolates. The Vienna/Hungarian/Brazilian clone and British EMRSA-3 clone were in circulation and a low frequency of single nucleotide polymorphisms (SNP) (≤20) differences was observed among isolates with the same spa-type.
The low number of SNP differences is suggestive of uninterrupted strain transmission and the persistence of t037-III-MRSA and t045-I-MRSA from 2013 to 2017 in the two studied hospitals. Alternative infection prevention and control strategies should be considered to supplement control efforts.
耐甲氧西林金黄色葡萄球菌（MRSA）是一种高度克隆的病原体，可在各种环境中引起感染。本研究的目的是确定来自南非两个地理位置不同的医院的具有相同 spa 型的医源性耐甲氧西林金黄色葡萄球菌（HA-MRSA）分离株是否基于 PFGE 在遗传上相关。此外，一小部分耐甲氧西林金黄色葡萄球菌分离株进行了 WGS 特征分析，然后与 PFGE 进行比较，以确定 PFGE 是否仍然是定义暴发和/或传播链的可靠方法。
血液培养物（BC）中分离出的金黄色葡萄球菌作为基于实验室的监测计划（GERMS-SA）的一部分提交给与医疗保健相关的感染、抗微生物药物耐药性和真菌感染中心（CHARM）。鉴定出的医源性耐甲氧西林金黄色葡萄球菌分离株进行了分子特征分析[葡萄球菌染色体盒（SCC）mec 和 spa 型]。对具有相同 spa 型的选定分离株进行脉冲场凝胶电泳（PFGE）。根据 spa 型、PFGE 聚类、分离时间和地点，从两个公共三级学术医院选择了 21 株耐甲氧西林金黄色葡萄球菌进行全基因组测序（WGS）。
从豪登省（GAU）和西开普省（WC）的两所公立三级学术医院采集的 529 株和 710 株分离株中，分别有 18%（n=95/529）和 33%（n=234/710）被鉴定为耐甲氧西林金黄色葡萄球菌。GAU 医院中最主要的克隆是 t037-III-MRSA（43.2%；n=41/95）。WC 医院中最主要的克隆是 t037-III-MRSA（23.9%，n=56/234）和 t045-I-MRSA（23.5%，n=55/234）。GAU-t037-III-MRSA 病例和 WC-t045-I-MRSA 病例发生在儿科患者人群中，而 WC-t037-III-MRSA 病例发生在成年患者人群中。GAU 医院检测到一种新型 spa 型（t19935）。PFGE 显示 GAU 和 WC-t037-III-MRSA 分离株在遗传上无法区分，以及大多数 WC-t045-I-MRSA 分离株也是如此。维也纳/匈牙利/巴西克隆和英国 EMRSA-3 克隆正在传播，并且在具有相同 spa 型的分离株中观察到单核苷酸多态性（SNP）（≤20）差异的频率较低。
SNP 差异数量较少表明 2013 年至 2017 年间，GAU 和 WC 研究医院中 t037-III-MRSA 和 t045-I-MRSA 的连续传播和持续存在。应考虑替代感染预防和控制策略来补充控制工作。
