Outbreak of gentamicin-resistant, meticillin-susceptible Staphlococcus aureus on a neonatal unit

Abstract

This report describes an outbreak of gentamicin-resistant, meticillin-resistant Staphylococcus aureus (GR MSSA) which occurred on a 21-bed neonatal unit (NNU) in Ninewells Hospital, Dundee, UK. An outbreak investigation was triggered by two new GR MSSA isolates from babies admitted directly to the NNU who had acquired this organism during their stay. Data on MSSA cases and antibiograms of patient isolates were flagged as an alert, and microbiology records were trawled to detect previous cases. Eight babies were affected by the outbreak strain over six months. Typing of all isolates by pulsed-field gel electrophoresis and spa typing showed that all were clonal complex 30, spa type t012. None of the outbreak strains were associated with bacteraemia, apart from one baby who was born at 24 weeks of gestation with a birth weight of 500g. Observation of practice and environmental swabbing of an incubator suggested that this was the most likely source of spread of the outbreak strain. Three of 11 surfaces sampled were positive for the outbreak strain. On inspection, it was found that the impeller was not removed routinely during cleaning, and debris was seen in the housing. Swabs that were taken from the impeller and housing yielded the outbreak strain. GR MSSA isolates from the NNU have been set up as an alert organism on the infection control system. No further cases were detected over one year of follow-up after full compliance with the new guidelines for cleaning and disinfection of incubators was implemented.