Prediction of surgical site infection in spine surgery from tests of nasal MRSA colonization and drain tip culture.

Abstract

MRSA is an organism that is a possible risk factor for postoperative SSI. The purpose of the study was to examine relationships among surgical site infection (SSI) after spinal surgery, nasal methicillin-resistant staphylococcus aureus (MRSA) colonization, and wound drain culture results. The subjects were 132 patients who underwent spinal instrumentation surgery. A preoperative nasal swab was used to check for the presence of MRSA colonization, and a wound drain tip culture was performed for detection of SSI. Data from culture studies using nasal samples and those from the distal tip of the wound drain were used for analysis. Five patients (3.8%) had nasal MRSA, 17 (13%) had positive drain tip cultures, 15 (11%) had SSIs, and 10 (8%) had SSIs with MRSA. Patients with nasal MRSA had a higher rate of detection of bacteria in the drain tip culture (40 vs. 19%, p = 0.065), and the SSI rate was significantly higher in patients with a positive drain tip culture (33 vs. 10%, p = 0.012). The total SSI rate differed significantly between patients with and without nasal MRSA (40 vs. 10%, p = 0.039); however, the SSI with MRSA rate did not differ significantly between these groups. MRSA carriers were not necessarily associated with MRSA infection, but were related to a positive drain tip culture and SSI, which might be due to endogenous skin bacteria. Therefore, possible SSI should be considered in patients with nasal MRSA colonization or bacteria detected in a drain tip culture.