Pulsed-field gel electrophoresis is a useful tool in the monitoring of methicillin-resistant Staphylococcus aureus epidemic outbreaks in the intensive care unit

We wished to determine how pulsed-field gel electrophoresis may be of use i n monitoring methicillin-resistant Staphylococcus aureus (MRSA) outbreaks i n the intensive care unit (ICU). A retrospective epidemiological analysis w as conducted. All 27 ICU patients and 11 patients from other hospital wards from whom MRSA was isolated over a one year period were included in the st udy. Seventeen of the 27 ICU MRSA isolates were analysed by pulsed-field ge l electrophoresis for clonality and compared with the 11 other hospital iso lates genotypes over the same period During three MRSA outbreaks, five MRSA genotypes were identified in ICU whilst the same five genotypes and three additional were found in the rest of the hospital Pulsed-field gel electrop horesis analysis was useful in identifying clonality of ICU MRSA infections and establishing that they were imported from hospital wards, rather than arising de novo in ICU. We were further able to identify clonal clusters wi thin the unit linked by temporal and geographical proximity suggestive of c ross-infection. Pulsed-field gel electrophoresis typing might be additional ly useful in tracing the source of human and/or environmental factors if a genotype were persistently identified.