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Purpose: The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization is increasing, and is an important pathogen in surgical site infections (SSI). Nasal-swab testing is effective for identifying patients with MRSA colonization, and has been shown to be predictive of SSI in cardiac and orthopedic surgery cases. However, the role of MRSA colonization on SSI following major gastrointestinal (GI) surgery is not known. The purpose of this study is to determine if MRSA colonization affects SSI after major GI surgery.

Methods: In 12/2007, we began universal nasal swab testing for MRSA colonization within 24hrs of admission. MRSA-colonized patients were placed on contact precautions and isolated. We retrospectively reviewed the charts of all patients undergoing major GI surgery (esophagus, stomach, hepatobiliary, pancreatic, duodenum, small bowel, colon and rectum) from 12/2007 to 8/2009. Patients were grouped according to nasal swab test results as MRSA-colonized (MRSA+), methicillin-sensitive Staphylococcus aureus-colonized (MSSA+) or not colonized (Negative). Data analyzed included demographics, incidence of SSI, organisms cultured from the wound, length of hospital stay (LOS) and mortality.

Results: A total of 1137 patients were identified and grouped according to nasal swab results; 897 (78.9%) Negative, 167 (14.7%) MSSA+, and 73 (6.4%) MRSA+. The mean age was 59.5 years, 44.5% were men, 47.9% had colon or rectal operations, and 9% were emergent operations. There with no significant difference between groups. There were 101 patients identified with SSI (8.9%), and the MRSA+ group was associated with a higher rate of SSI when compared to Negative and MSSA+ groups (13.7% vs. 9.4% vs. 4.2%; p<0.05). Wound culture results were identified in 92 (91.1%) patients with SSI. When SSI was present the MRSA+ group had a significantly higher rate of MRSA positive wound cultures when compared to non-MRSA colonized patients (70% [7/10] vs. 8.5% [7/82]; p<0.0001). The mean LOS was 12.5 days for MRSA+ group, and was 4 days longer than Negative and MSSA+ groups (8.8 and 7.6 days, respectively; p<0.001). Although the presence of SSI significantly increased LOS from 6.2 days to 15.7 days (p<0.001), there was no difference in LOS for patients with SSI between nasal swab groups (p=9.2). Overall mortality was 4.0% (45/1137) and deaths were evenly distributed between nasal-swab groups.

Conclusions: Our data suggest that MRSA nasal colonization is associated with a longer LOS and an increase in incidence of SSI in patients undergoing major GI surgery. Furthermore, when SSI occurred, MRSA nasal colonization was strongly predictive of MRSA-associated SSI. Preoperative nasal swab test with decolonization of MRSA+ patients may decrease LOS and reduce the incidence of MRSA-associated SSI after major GI surgery. A cost benefit analysis is required.