Antimicrobial Drugs and Community-acquired Methicillin-Resistant Staphylococcus aureus, United Kingdom

We report results of a case–control study of the association between receipt of antimicrobial agents and diagnosis of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) in the United Kingdom. Eligible adults, selected from the General Practice Research Database, had no previous diagnosis of MRSA, no hospitalization in the past 2 years, and >2 years of follow-up recorded in the database. For 2000–2004, we identified 1,981 MRSA case-patients and 19,779 matched control-patients. The odds ratios (ORs) and 95% confidence intervals (CIs) of MRSA diagnosis for patients who were prescribed 1, 2–3, or >4 antimicrobial drugs were 1.57 (CI 1.36–1.80), 2.46 (CI 2.15–2.83), and 6.24 (CI 5.43–7.17), respectively. Risk for community-acquired MRSA increased with number of antimicrobial drug prescriptions, appeared to vary according to antimicrobial drug classes prescribed the previous year, and was highest for quinolones (OR 3.37, CI 2.80–4.09) and macrolides (OR 2.50, CI 2.14–2.91).