Temporal relationship between prevalence of meticillin-resistant Staphylococcus aureus (MRSA) in one hospital and prevalence of MRSA in the surrounding community: a time-series analysis

SummaryWe studied the relationship between meticillin-resistant Staphylococcus aureus (MRSA) prevalence in the Aberdeen Royal Infirmary and in the surrounding community (Grampian region: 500 000 inhabitants). We calculated the monthly %MRSA for both hospital and community from January 1996 to February 2002. A dynamic regression model was adjusted to measure any relationship between both series. The monthly %MRSA in the community was strongly related to the monthly %MRSA observed one month before in the hospital (R2 = 90.8%). We found no relationship with antimicrobial community use, although we have previously reported a strong correlation between prior use of antibiotics and incidence of MRSA in the hospital. By using time-series analysis techniques, we demonstrated that variations in MRSA prevalence in the hospital are quickly followed by similar variations in MRSA prevalence in the surrounding community. These results suggest that the reason for the increase in MRSA prevalence in the community was a hospital MRSA outbreak. Screening at patient discharge should be evaluated as a new measure to control spread of MRSA in the community.