Post-operative deep sternal wound infections: making an early microbiological diagnosis

Early microbiological diagnosis of deep sternal wound infections (DSWI) could improve outcomes by allowing targeted antibiotic treatment. This study aims to analyse the utility of superficial sternal wound swabs and blood cultures.

From January 2005 to June 2011, 70 patients were prospectively identified with DSWI. Microbiological data were obtained retrospectively to study the correlation between superficial sternal swabs, blood cultures and the final culture results from deep sternal tissue. Colonization with multi-resistant organisms (MROs) was also analysed for its significance in the microbiological aetiology of DSWI. Patient characteristics were obtained to analyse predictors of infection caused by specific groups of organisms.

Superficial swabs predicted the pathogen 75% of the time (n = 43). Specific to Staphylococcus aureus (n = 27), the positive predictive value of a superficial sternal swab was found to approach 100%. Colonization with MRO is 100% predictive of the pathogen in DSWI. The absence of gram-negative organisms from superficial swabs or blood cultures (n = 48) has a negative predictive value of 98%. The inclusion of blood cultures predicted the pathogen 82% of the time across all types of bacterial infections. Patient characteristics did not appear to predispose to infections caused by specific groups of organisms.

Superficial swabs and blood cultures appear to be useful in establishing the microbiological aetiology of DSWI. Routing testing and reporting of these samples could enable early and targeted antimicrobial therapy in DSWI to improve outcomes.