Healthcare-associated outbreak of meticillin-resistant Staphylococcus aureus bacteraemia: role of a cryptic variant of an epidemic clone

Miller, R M, Price, J R, Batty, E M, Didelot, X, Wyllie, D, Golubchik, T, Crook, D W, Paul, J, Peto, T E A, Wilson, D J, Cule, M, Ip, C L C, Day, N P J, Moore, C E, Bowden, R and Llewelyn, M J (2014) Healthcare-associated outbreak of meticillin-resistant Staphylococcus aureus bacteraemia: role of a cryptic variant of an epidemic clone. Journal of Hospital Infection, 86 (2). pp. 83-89. ISSN 0195-6701

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Abstract

BACKGROUND

New strains of meticillin-resistant Staphylococcus aureus (MRSA) may be associated with changes in rates of disease or clinical presentation. Conventional typing techniques may not detect new clonal variants that underlie changes in epidemiology or clinical phenotype.

AIM

To investigate the role of clonal variants of MRSA in an outbreak of MRSA bacteraemia at a hospital in England.

METHODS

Bacteraemia isolates of the major UK lineages (EMRSA-15 and -16) from before and after the outbreak were analysed by whole-genome sequencing in the context of epidemiological and clinical data. For comparison, EMRSA-15 and -16 isolates from another hospital in England were sequenced. A clonal variant of EMRSA-16 was identified at the outbreak hospital and a molecular signature test designed to distinguish variant isolates among further EMRSA-16 strains.

FINDINGS

By whole-genome sequencing, EMRSA-16 isolates during the outbreak showed strikingly low genetic diversity (P < 1 × 10(-6), Monte Carlo test), compared with EMRSA-15 and EMRSA-16 isolates from before the outbreak or the comparator hospital, demonstrating the emergence of a clonal variant. The variant was indistinguishable from the ancestral strain by conventional typing. This clonal variant accounted for 64/72 (89%) of EMRSA-16 bacteraemia isolates at the outbreak hospital from 2006.

CONCLUSIONS

Evolutionary changes in epidemic MRSA strains not detected by conventional typing may be associated with changes in disease epidemiology. Rapid and affordable technologies for whole-genome sequencing are becoming available with the potential to identify and track the emergence of variants of highly clonal organisms.

Item Type: Article
Schools and Departments: Brighton and Sussex Medical School > Global Health and Infection
Subjects: R Medicine
Depositing User: Sandy Gray
Date Deposited: 15 Sep 2014 12:03
Last Modified: 04 Aug 2017 18:25
URI: http://sro.sussex.ac.uk/id/eprint/49930

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