Nasal carriage of Staphylococcus aureus in patients undergoing Mohs micrographic surgery is an important risk factor for postoperative surgical site infection: A prospective randomised study

Background Surgical site infection (SSI) can be a problematic complication of Mohs micrographic surgery (MMS). Previous reports have cited nasal Staphylococcus aureus (S.aureus) carriage as a risk factor for SSI, but none thus far in dermatologic surgery. Objective The aim was to determine the difference in infection rates between nasal carriers of S.aureus and non-carriers, and whether decolonisation with intranasal mupirocin ointment and chlorhexidine wash would reduce the infection rate in nasal carriers. Methods In all, 738 patients presenting for MMS at the Oxford Day Surgery and Dermatology underwent a nasal swab to determine their S.aureus carriage status. S.aureus carriers were randomised for decolonisation with intranasal mupirocin ointment and chlorhexidine body wash. Non-carriers were untreated. All patients were followed up for SSI. Results The rate of SSI was 11 per cent in untreated S.aureus carriers, 4 per cent in treated carriers, and 3 per cent in non-carriers. The difference in infection rate between carriers and non-carriers was significant (P<0.001). The difference between treated and untreated carriers was also significant (P=0.05). Conclusion Nasal S.aureus carriage is an important risk factor for SSI in MMS, conferring an over threefold increase in SSI risk. A pre-operative nasal swab provides a simple and effective risk stratification tool. The use of a topical decolonisation regimen reduces the infection rate in carriers to a level approaching non-carriers without exposure to systemic antibiotics.