Temporal trends and epidemiology of Staphylococcus aureus surgical site infection in the Swiss surveillance network: a cohort study

Abstract

Staphylococcus aureus is the leading pathogen in surgical site infections (SSI). To explore trends and risk factors associated with S.aureus SSI. Risk factors for monomicrobial S.aureus SSI were identified from the Swiss multi-centre SSI surveillance system using multi-variate logistic regression. Both in-hospital and postdischarge SSI were identified using standardized definitions. Over a six-year period, data were collected on 229,765 surgical patients, of whom 499 (0.22%) developed monomicrobial S.aureus SSI; 459 (92.0%) and 40 (8.0%) were due to meticillin-susceptible S.aureus (MSSA) and meticillin-resistant S.aureus (MRSA), respectively. There was a significant decrease in the rate of MSSA SSI (P=0.007), but not in the rate of MRSA SSI (P=0.70). Independent protective factors for S.aureus SSI were older age [≥75 years vs <50 years: odds ratio (OR) 0.60, 95% confidence interval (CI) 0.44-0.83], laparoscopy/minimally invasive surgery (OR 0.68, 95% CI 0.50-0.92), non-clean surgery [OR 0.78 (per increase in wound contamination class), 95% CI 0.64-0.94] and correct timing of pre-operative antibiotic prophylaxis (OR 0.80, 95% CI 0.65-0.98). Independent risk factors were male sex (OR 1.38, 95% CI 1.14-1.66), higher American Society of Anesthesiologists' score (per one-point increment: OR 1.30, 95% CI 1.13-1.51), re-operation for non-infectious reasons (OR 4.59, 95% CI 3.59-5.87) and procedure type: cardiac surgery, laminectomy, and hip or knee arthroplasty had two-to nine-fold increased odds of S.aureus SSI compared with other procedures. SSI due to S.aureus are decreasing and becoming rare events in Switzerland. High-risk procedures that may benefit from specific preventive measures were identified. Unfortunately, many of the independent risk factors are not easily modifiable.