Report of a hospital neonatal unit outbreak of community-associated methicillin-resistant Staphylococcus aureus

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) with the type IV staphylococcal chromosomal cassette mec (SCCmec) is rarely reported as being acquired in hospital. We report a hospital outbreak, in Grampian, Scotland, of eight cases of skin and soft-tissue infections due to such a strain. All patients had been in the labour, delivery and maternity units of a small community hospital during a 7-month period. Typing by pulsed-field gel electrophoresis showed the isolates to be a single strain closely related to the USA800 lineage (paediatric clone) and additional typing confirmed it as ST5-MRSA-IV. Genes for exfoliative toxin A (ETA) and enterotoxin D were detected by PCR in all the isolates although none carried the Panton-Valentine leukocidin gene. Region-wide surveillance of over 6000 MRSA isolates collected from 1998 to 2004 showed that 95 (1.6%) were closely related to the outbreak strain although only 60 carried the ETA gene. The strain has not been seen elsewhere in Scotland.