Here is an article on MRSA colonization and surgical site infection published recently in Infection Control and Hospital Epidemiology.
Using a retrospective cohort study design of Veterans Affairs (VA) Boston patients, the investigators determined whether preoperative nasal MRSA carriage was a significant predictor of postoperative infections, after accounting for surgical infection risk and surgical prophylaxis.
Multivariate analysis of risk factors for each outcome was performed. Among 4,238 eligible patients, 279 (6.6%) were positive for preoperative nasal MRSA. After adjustment for surgery type, vancomycin prophylaxis, chlorhexidine/alcohol surgical skin preparation, and SSI risk index, preoperative nasal MRSA was significantly associated with postoperative MRSA cultures (infections). Strikingly, Vancomycin prophylaxis was associated with an increased risk of total SSI in nasal MRSA negative patients (RR, 4.34; 95% CI, 2.19-8.57) yet was protective for patients positive for nasal MRSA (RR 0.61; 95% CI 0.06-5.75).
So, preoperative nasal MRSA colonization was independently associated with MRSA clinical cultures in the postoperative period. Vancomycin prophylaxis increased the risk of total SSI in nasal MRSA-negative patients yet was protective in MRSA positive patients.
This was an observational, retrospective study, so causality cannot be determined.
Regardless, this is perplexing.
