The Risk of Infection after Nasal Colonization with Staphylococcus Aureus

Purpose: Nasal, axillary, or inguinal colonization with Staphylococcus aureus generally precedes invasive infection. Some studies have found that colonization with methicillin-resistant S. aureus (MRSA) poses a greater risk of clinical infection than colonization with methicillin-susceptible S. aureus (MSSA). However, the magnitude of risk is unclear. Methods: We undertook a systematic review to provide an overall estimate of the risk of infection following colonization with MRSA compared with colonization by MSSA. Ten observational studies, with a total of 1170 patients, were identified that provided data on both MSSA and MRSA colonization and infection. A random-effects model was used to obtain pooled estimates of the odds ratio and 95% confidence interval. Results: Overall, colonization by MRSA was associated with a 4-fold increase in the risk of infection (odds ratio 4.08, 95% confidence interval, 2.10-7.44). Studies differed in the choice of patient population, severity of illness, and frequency of sampling to detect colonization. Conclusion: Further research is needed to identify effective methods for sustained eradication of MRSA carriage to reduce the high risk of subsequent infection.