MRSA acquisition in an intensive care unit

Background: This paper describes a retrospective investigation of methicillin-resistant Staphylococcus aureus (MRSA) acquisition in an 8-bed intensive care unit (ICU) over a 5-month period. Methods: Clinical and microbiologic data were collected from the ICU, including MRSA detection dates, patient dependency scores, standardized environmental screening data, weekly bed occupancies, number of admissions, and nurse staffing levels. MRSA acquisition weeks were defined as weeks during which initial delivery of MRSA occurred before sampling and laboratory confirmation. Weekly workloads were plotted against staffing levels and modelled against MRSA acquisition weeks and hygiene failures. Results: Of 174 patients admitted into the ICU, 28 (16 %) were found to have MRSA; 12 of these (7 %) acquired MRSA on the ICU within 7 of the 23 weeks studied. Six of these 7 weeks were associated with a deficit of trained nurses during the day and 5 with hygiene failures (data unavailable for 2). Pulsed-field gel electrophoresis (PFGE) profiles demonstrated relationships between staphylococci from staff hands, hand-touch sites, and patients' blood. Conclusion: MRSA acquisition in the ICU was temporally associated with reduced numbers of trained nurses and hygiene failures predominantly involving hand-touch sites. Epidemiologic analysis suggested that patient acquisitions were 7 times more likely to occur during periods of nurse understaffing.