Does antibiotic exposure increase the risk of methicillin-resistant Staphylococcus aureus (MRSA) isolation? A systematic review and meta-analysis

Background Current evidence does not provide a clear definition of the association between methicillin-resistant Staphylococcus aureus (MRSA) isolation and previous antibiotic use. A systematic review was performed to determine whether antibiotic exposure is a risk factor for the isolation of MRSA. Methods MEDLINE and EMBASE databases were searched to identify studies published between 1976 and 2007 on the role of antibiotics as a risk factor for MRSA isolation in adult patients. The outcome of interest was MRSA isolation. Summary statistics were risk ratios (RR) comparing MRSA-positive patients to those without S. aureus isolation or with methicillin-susceptible S. aureus isolation. Results Seventy-six studies, including a total of 24 230 patients, met the inclusion criteria. Antibiotic exposure was determined in the 126 ± 184 (mean ± SD) days preceding MRSA isolation. The risk of acquiring MRSA was increased by 1.8-fold [95% confidence interval (CI), 1.7–1.9; P < 0.001] in patients who had taken antibiotics. The RR for single classes of antibiotics was 3 (95% CI, 2.5–3.5) for quinolones, 2.9 (95% CI, 2.4–3.5) for glycopeptides, 2.2 (95% CI, 1.7–2.9) for cephalosporins and 1.9 (95% CI, 1.7–2.2) for other β-lactams. Significant heterogeneity was detected among studies. A regression analysis revealed that the heterogeneity was linked to the length of time in which antibiotic exposure was detected before MRSA isolation (more or less than 180 days). Conclusions This meta-analysis shows a clear association between exposure to antibiotics and MRSA isolation. This information may be useful for researchers in designing future studies and for policy decision-making on the appropriate management of antibiotic therapies.