Beukers Alicia G, Newton Peter, Hudson Bernard, Ross Kimberly, Gottlieb Thomas, O'Sullivan Matthew, Daley Denise A, Pang Stanley, Coombs Geoffrey W, van Hal Sebastiaan J
NSW Health Pathology, Department of Infectious Diseases and Microbiology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia.
NSW Health Pathology, Microbiology, Wollongong Hospital, Wollongong, NSW, Australia.
J Antimicrob Chemother. 2020 May 1;75(5):1112-1116. doi: 10.1093/jac/dkz560.
Early identification of MRSA by diagnostic medical microbiology laboratories enables improved antimicrobial choice and outcomes. The Cepheid Xpert® MRSA/SA BC test rapidly identifies Staphylococcus aureus bloodstream infections through spa gene detection and methicillin resistance via mecA gene detection. Recent emergence of S. aureus with deletions in the spa gene has resulted in false-negative results for this test, leading to misidentification of infections with this organism, particularly MRSA ST45.
To investigate the emergence and prevalence of ST45 MRSA in New South Wales (NSW), Australia.
WGS read data from six NSW hospitals were collected for 131 ST45 MRSA isolates and analysed.
Of the 131 ST45 MRSA investigated, 88.5% (116/131) contained a deletion in the spa gene that appeared to have arisen once in approximately 2010 followed by clonal expansion. Given the successful establishment of this 'spa-deletion' MRSA clone, the Cepheid Xpert® MRSA/SA BC test became unreliable for confirming S. aureus bacteraemia in NSW. Subsequently, the algorithm used by this test has been updated and evaluated to take into account the presence of S. aureus with either a spa deletion or SCCmec target variations.
This study highlighted the applied use of WGS for assessing diagnostic assays and informing necessary changes to ensure the viability of the Cepheid Xpert® MRSA/SA BC test in the context of the new 'spa-deletion' MRSA clone. It demonstrated how continued surveillance through WGS can reveal evolutionary events that may impact diagnostic assays, allowing corrective modifications to be made in real time.
诊断医学微生物实验室对耐甲氧西林金黄色葡萄球菌（MRSA）的早期识别有助于优化抗菌药物选择并改善治疗结果。赛沛Xpert® MRSA/SA BC检测通过检测spa基因快速识别金黄色葡萄球菌血流感染，并通过检测mecA基因确定甲氧西林耐药性。最近出现的spa基因缺失的金黄色葡萄球菌导致该检测出现假阴性结果，从而导致对该菌感染的错误识别，尤其是MRSA ST45。
调查澳大利亚新南威尔士州（NSW）ST45 MRSA的出现情况和流行率。
收集了来自新南威尔士州六家医院的131株ST45 MRSA分离株的全基因组测序读取数据并进行分析。
在调查的131株ST45 MRSA中，88.5%（116/131）含有spa基因缺失，该缺失似乎在2010年左右出现一次，随后进行克隆扩增。鉴于这种“spa缺失”MRSA克隆的成功建立，赛沛Xpert® MRSA/SA BC检测在新南威尔士州确认金黄色葡萄球菌菌血症时变得不可靠。随后，该检测所使用的算法已更新并进行评估，以考虑存在spa缺失或SCCmec靶点变异的金黄色葡萄球菌。
本研究强调了全基因组测序在评估诊断检测以及告知必要更改以确保赛沛Xpert® MRSA/SA BC检测在新的“spa缺失”MRSA克隆背景下的可行性方面的应用。它展示了通过全基因组测序持续监测如何揭示可能影响诊断检测的进化事件，从而允许实时进行纠正性修改。
