Risk factors for surgical site infection after cardiac surgery: the role of endogenous flora

The study's objective was to assess predictors of surgical site infection (SSI) after cardiac surgery and the relationship of perioperative nasal carriage of Staphylococcus species with the development of SSI.

Surveillance for infections was performed, and anterior nares cultures of patients who underwent cardiac surgery were obtained. Preoperative risk factors were analyzed, and staphylococcal isolates from nares and SSI were compared using pulsed-field gel electrophoresis.

Twelve patients had 14 SSIs (5.7 infections/100 surgeries). Two risk factors were significantly associated with SSI: smoking (P = .002, confidence interval(95) 1.1-1.4, relative risk = 1.3) and increased body mass index (P = .003, confidence interval(95) 2.8-99.8, relative risk = 16.8). A total of 5 of 8 infected patients (62.5%) for whom nares cultures were available had identical strains in their nares and SSI.

Smoking and body mass index were predictors of SSI. Approximately 2 of 3 infected patients for whom nares cultures were obtained had an SSI that was likely from an endogenous source.