METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS - INVESTIGATION OF A HOSPITAL OUTBREAK USING A CASE-CONTROL STUDY

A retrospective case-control study of 50 MRSA-positive patients was ca rried out during an outbreak of methicillin-resistant Staphylococcus a ureus (MRSA) at an acute general hospital in London. Controls were ran domly selected from MRSA-negative patients admitted during the outbrea k period. Risk factors investigated included length of admission prior to screening, number of ward changes, main diagnosis, extent of staff contact, pressure sores, surgical and other invasive procedures and a ntibiotic treatment. Outcome variables examined were rates of infectio n (versus colonization) with MRSA and mortality. Patients with MRSA we re in hospital longer before microbiological specimens were taken and moved wards more often than controls. In a logistic regression analysi s, length of stay in hospital, pressure sores, physiotherapy and surgi cal procedures were associated with a significantly increased risk of acquiring MRSA. Odds ratios (and 95% confidence intervals) for having acquired MRSA were: 8.3 (1.02-71.43) if a patient had pressure sores; 3.7 (1.10-12.5) if they received physiotherapy; and 3.2 (1.82-10.0) if they underwent surgical procedures. The rate of clinical infection am ongst patients with this strain of MRSA was 26% and included life-thre atening infections such as septicaemia, underlining the potential viru lence of MRSA. Surgery and physiotherapy may have been markers of debi lity. Physiotherapy was probably a marker of increased rates of contac t with all hospital staff, and high standards of hand hygiene should b e promoted amongst all staff as the most important factor in controlli ng an outbreak of MRSA. Good bed management is essential for hospital infection control.