Genomic Surveillance of MRSA associated with bloodstream infection in England

Abstract

Background: Mandatory reporting of MRSA blood stream infections (BSI) has occurred in England for over 15 years. Epidemiological information is recorded, but routine collection of isolates for characterisation has not been undertaken. Simultaneously, developments in whole-genome sequencing (WGS) have enabled it to be used for investigation of outbreaks and spread of antimicrobial resistance, and to determine bacterial population structure. The potential benefits of adding genomics to epidemiological surveillance are unknown. Methods: We conducted a combined epidemiological and genomic survey of MRSA BSI in England over a one-year period, to determine the feasibility and potential utility of this approach. Results: 903 cases of MRSA BSI were reported during the study period, and 425 isolates were available for sequencing. 276 (65%) isolates were clonal complex (CC) 22. Addition of a further 64 MRSA genomes from published outbreak investigations, showed that the study genomes could provide context for outbreak isolates and supported cluster identification. Comparison to other MRSA collections demonstrated variation in the clonal diversity achieved through different sampling strategies, and identified potentially high-risk clones such as USA300, and a local expansion of CC5 MRSA in the South West region. Conclusions: This study demonstrates the potential utility of combined epidemiological and genomic MRSA BSI surveillance in determining the national population structure of MRSA, contextualising previously recognised MRSA outbreaks, and in detection of potentially high-risk lineages. These findings support the integration of epidemiological and genomic surveillance for MRSA BSI as a first step towards a comprehensive surveillance programme in England.