Simon R. Harris, PhD, from the Wellcome Trust Sanger Institute in Cambridge, U.K., and colleagues assessed the use of whole-genome sequencing to enhance MRSA detection by studying a putative MRSA outbreak on a special care baby unit (SCBU) at a National Health Service Foundation Trust in Cambridge. Findings from an infection-control team through conventional analysis of data were validated and expanded. Isolates from all colonized patients in the SCBU, and MRSA isolates from patients in the hospital or community with the same antibiotic susceptibility profile, were sequenced.In a six-month period in 2011, the hospital infection-control team identified 12 infants colonized with MRSA, but could not confirm a persistent outbreak. The researchers identified 26 related cases of MRSA carriage using whole-genome sequencing, and demonstrated transmission within the SCBU, between postnatal mothers, and within the community. The MRSA type from the outbreak was identified as a new sequence type (ST) 2371, closely related to ST22. Based on sequencing data, it was confirmed that MRSA carriage by a staff member had allowed the outbreak to persist during periods without known infection on the SCBU and after a deep clean.