Hospital MRSA outbreaks: Multiplex PCR-reverse line blot binary typing as a screening method for WGS, and the role of the environment in transmission.

Abstract

Whole-genome sequencing (WGS) can provide useful information on methicillin-resistant Staphylococcus aureus (MRSA) transmission in hospitals. However, it is expensive and laborious, especially for environmental screening programs which generate large numbers of isolates. Multiplex PCR-reverse line blot binary typing (mPCR-RLB BT) is a rapid, high throughput, inexpensive typing method which could be useful to screen isolates for WGS. This study assessed the strategy of screening isolates with mPCR-RLB BT to reduce the need for WGS; and to assess the role of the environment in transmission. MRSA transmission in a Burns Unit and its related Intensive Care Unit was studied. mPCR-RLB BT was performed on 238 isolates; this, combined with epidemiological data, was used to choose 97 isolates for WGS. Relationships between isolates by WGS demonstrated several outbreaks. There was a significant contribution of environmental isolates to transmission, and several problem areas were identified. There was a substantial cost saving from screening isolates with mPCR-RLB BT. The use of an inexpensive, rapid screening method for MRSA typing is useful to reduce expenditure and time spent on hospital infection control programs, and reductions are likely to be even more considerable in a non-outbreak setting. Environmental screening and WGS are useful to determine exact sources of transmission to focus mitigation strategies.