Dealing with Sternal Wound Healing Disorders after Cardiac Surgery: Bacterial Spectrum and Implications for Antibiotic Therapy

Introduction: Sternal wound infections are a serious complication after cardiac surgery resulting in increased morbidity and mortality. Antimicrobial therapy is essential for successful treatment.

Methods: Between May 2016 and May 2017, a total number of 65 patients were enrolled into a prospective wound database. In this database, patients with a sternal wound infection requiring operative revision after cardiac surgery with full sternotomy were involved.

Results: Regarding the baseline characteristics, patients mean age was 66 years, the mean BMI was 30, 23% suffered from chronic obstructive pulmonary disease and 46% from diabetes. Bilateral internal thoracic artery grafting was performed in 14% of these patients. In 52% of the microbiological swabs taken intraoperatively no contamination was found. In over 53% of the positive swabs, coagulase negative staphylococci (CoNS) were identified, in 13% staphylococcus aureus and in 10% enterococcus spp. In 99% of the swabs positive for CoNS, staphylococcus epidermidis was observed. These strains were resistant to Clindamycin in 86%, but in all cases susceptible for Linezolid and Vancomycin. The overall in-hospital mortality was 10%, a successful treatment with discharge from hospital could be reached in 69% (N = 45) of the cases. In a total of 13 patients (20%), plastic surgery was necessary and of these patients, 3 died (15%). In 56% of these 13 patients, CoNS were detected in the swabs of the first operation. In all cases, these CoNS were resistant to clindamycin.

Conclusion: Sternal wound infections remain a challenging complication after cardiac surgery. CoNS are the most frequent pathogens and in contrast to recent literature the local resistance rate for clindamycin was significantly higher. Thus, clindamycin should not be considered as an empirical first line therapy. When choosing an empirical antibiotic, the local pathogen spectrum needs to be taken into account in accordance with the germ identification and resistance testing.