Moore G, Cookson B, Gordon N C, Jackson R, Kearns A, Singleton J, Smyth D, Wilson A P R
Clinical Microbiology and Virology, University College London Hospitals NHS Foundation Trust, London, UK; Biosafety Investigation Unit, Public Health England, Porton Down, Salisbury, UK.
Staphylococcus Reference Unit, Antimicrobial Resistance and Healthcare Associated Infections, Public Health England Colindale, London, UK; Division of Infection and Immunity, University College London, London, UK.
J Hosp Infect. 2015 May;90(1):38-45. doi: 10.1016/j.jhin.2014.12.014. Epub 2015 Jan 13.
In order to study the micro-epidemiology of meticillin-resistant Staphylococcus aureus (MRSA) effectively, the molecular typing method used must be able to distinguish between different MRSA strains. Pulsed-field gel electrophoresis (PFGE) can detect small genetic differences but is limited in its potential to distinguish isolates within a major lineage. Whole-genome sequencing (WGS) provides sufficient resolution to support or exclude links between otherwise indistinguishable isolates, but lacks the practical utility of conventional typing methods.
To explore the utility of WGS in a hierarchical approach with PFGE to help establish possible sources of MRSA cross-transmission in the intensive care setting.
Possible transmission routes from donor to recipient via the hands of staff, the air or environmental surfaces were identified. Focused molecular typing used PFGE to explore these transmission hypotheses. WGS was applied when an acquisition event involved a common PFGE pulsotype.
Thirty-eight of the 78 acquisition events could not be explored as clinical isolates were not available. PFGE excluded all potential donors from 26 of the remaining 40 acquisition events, but did identify a probable source in 14 new colonizations. Within the hypotheses tested, PFGE supported links between patients occupying the same bay, the same bed space, adjacent isolation rooms and different wards. When a patient source was not identified, PFGE implicated the ward environment and the hands of staff. However, WGS disproved three of these transmission pathways.
WGS can complement conventional typing methods by confirming or refuting possible MRSA transmission hypotheses. Epidemiological data are crucial in this process.
为了有效地研究耐甲氧西林金黄色葡萄球菌（MRSA）的微观流行病学，所使用的分子分型方法必须能够区分不同的MRSA菌株。脉冲场凝胶电泳（PFGE）能够检测到微小的基因差异，但在区分主要谱系内的分离株方面潜力有限。全基因组测序（WGS）提供了足够的分辨率来支持或排除原本难以区分的分离株之间的关联，但缺乏传统分型方法的实际效用。
探讨将WGS与PFGE分级联用的效用，以帮助确定重症监护环境中MRSA交叉传播的可能来源。
确定了从供体经工作人员的手、空气或环境表面传播给受体的可能传播途径。采用PFGE进行针对性分子分型，以探究这些传播假设。当感染事件涉及常见的PFGE脉冲型时，应用WGS。
78例感染事件中有38例因无法获得临床分离株而无法进行探究。PFGE排除了其余40例感染事件中26例的所有潜在供体，但在14例新定植病例中确定了一个可能的来源。在所测试的假设中，PFGE支持了同一病房、同一床位、相邻隔离病房和不同病房的患者之间的关联。当未确定患者来源时，PFGE表明病房环境和工作人员的手有问题。然而，WGS否定了其中三条传播途径。
WGS可以通过证实或反驳可能的MRSA传播假设来补充传统分型方法。在此过程中，流行病学数据至关重要。
