The population impact of MRSA in a country: the national survey of MRSA inWales, 1997

Continuous data collection on all new isolates of MRSA via CoSurv has taken place in Wales since January 1996. In order to audit this data collection, and to address some of the issues that it does not include, a survey of MR SA was carried out. Questionnaires were completed by infection control team s. Rates were calculated using hospital throughput denominators. Results fr om the one-day prevalence survey, the two-week incidence survey, and the fo llow-up survey carried out on new MRSA patients identified in the incidence survey, are presented. Results were found to be broadly similar to those c ollected via routine surveillance, MRSA was found frequently and disproport ionately in the elderly, with higher rates in male than female patients. Th e highest incidence of total and invasive MRSA was in males aged 75 and ove r (total: 12.5/1000 finished consultant episodes; invasive: 2.8/1000). Alth ough there was a large community reservoir of MRSA, most appeared to hale b een acquired in hospital, since most patients had a history of hospitalizat ion, often with multiple hospital admissions. Community-based isolates from cases with no hospital history tended to have been from ulcers. Prevalence and incidence of MRSA was relatively low compared with hospital throughput (mean prevalence: 2.4/100 occupied beds; mean incidence: 3.6/1000 finished consultant episodes), there was also quite large variation between sites, even when screening samples were removed. Patients with MRSA had strikingly long stays before isolation of the organism (prevalence survey: 39 days; i ncidence survey: 31 days) and highest incidence occurred in elderly care wa rds. The outcome survey showed that approximately half of the patients M-er e treated with some type of antimicrobial therapy for MRSA. Decontamination therapy was associated with clearance of MRSA only when controlling for se x of the patient. The majority of patients were discharged still with MRSA, mostly to their own homes. The survey emphasizes the need to continue surv eillance to detect any changes, to allow guidelines based on evidence to be developed and to monitor the effectiveness of such guidelines. (C) 2000 Th e Hospital Infection Society.