Reviewed by Cindy Noyes
Bottom line: SA carriage, particularly in the nares, raises risk for SA SSI and supports efforts for pre-operative screening for the presence of SA and decolonization.
Troeman and colleagues aimed to quantify the association of staphylococcus aureus (SA) carriage with SA surgical site infection (SSI) or post operative blood stream infection (BSI). They used data from the prospective observational trial ASPIRE-SSI, a multi-national, multi-center group of adults undergoing multiple different surgeries in Europe. Participants were screened with swabs of nares, throat and perineum within 30 days of their procedure and semi-quantitative cultures performed. Subjects were excluded if active SA infection present or concomitant participation in anti-staphylococcal intervention. Propensity scoring was performed to adjust for confounders, which included age, sex, BMI, prior colonization, pre-op decolonization, immunosuppression, Charlson Comorbidity score, ASA, site and the comparison group was composed of noncarriers. The main outcome measured was SA SSI or BSI within 90 days of the procedure. Of the 10,0691 patients screened, 5004 were included in the cohort. Of these, 3369 or 67% were colonized; 35% of the original 10,000 participants. Surgeries performed included cardiothoracic, knee and hip arthroplasty, among others. One hundred SSI/BSIs occurred; 91 SSIs, 4 BSIs, 5 SSIs with secondary BSI. Of these, 86 occurred in SA carriers, revealing a cumulative incidence of 2.6 per 100 carriers (compared to a cumulative incidence of 0.5 per 100 non carriers). SA carriage at any site and nasal carriage were independently associated with SSI. Extra-nasal carriage alone was not an independent risk factor. Risk of SSI/BSI increased as the number of pre-operative colonized bodily sites increased. Additionally, burden of colonization correlated with rising risk, thus for every incremental unit increase in bacterial load recovered via nares culture (range 0 growth to 4+ growth), adjusted HR for developing SSI/BSI increased 1.23-fold. Nasal SA bacterial load increased as the number of colonized body sites increased. Only 4 of these were MRSA infections, so no meaningful subgroup analysis could be conducted.
Reference: Troeman D, et al. Association of S. aureus bacterial load and colonization sites with the risk of Post op S aureus infection. OFID. July 2024; https://doi.org/10.1093/ofid/ofae414.