Risk factors for Staphylococcus aureus surgical site infection during an outbreak in patients undergoing cardiovascular surgery

BackgroundThis study examined the epidemiology of an outbreak of Staphylococcus aureus surgical site infections (SSI) after cardiovascular surgery, and analyzed risk factors for S aureus SSIs.MethodsThis was a retrospective case-control study to determine risk factors for S aureus SSI in 38 patients who developed S aureus SSI during the outbreak period, compared with age-, sex-, and procedure-matched controls. S aureus strains were typed by pulsed-field gel electrophoresis.ResultsA total of 38 patients had S aureus SSI. Pulsed-field gel electrophoresis identified transmission of 3 S aureus clones (2 MSSA clones and 1 MRSA clone). Twenty-one health care workers were carriers of outbreak strains. In multivariate analysis, the significant risk factors for S aureus SSI were previous cardiac surgery (odds ratio, 7.41; 95% confidence interval, 1.05–52.16) and long procedure duration (odds ratio, 1.49; 95% confidence interval, 1.00–2.21).ConclusionsThis outbreak demonstrates evidence of nosocomial transmission of 3 clones of S aureus in the setting of incomplete compliance with recommended standard perioperative infection control measures, associated with a high prevalence of staff carriage of the predominant outbreak strains.