The endogenous pathway is a major route for deep sternal wound infection

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Abstract
Objective: Deep wound infections pose an increasing problem in cardiac surgery patients. Prospective infection monitoring is thus a means of identifying possible risk factors. Methods: Within a period of 5 months, a total of 376 adult patients, 260 men and 116 women, with a mean age of 62.6 years (range 18–88), underwent coronary bypass grafting (n=281) or other cardiac surgery procedures (n=95). Nasal cultures were taken preoperatively from every patient, as well as cultures of the wound during surgery and when dressings were changed thereafter. In addition, nasal cultures were taken from all the medical and nursing staff. To differentiate endogenous and exogenous infection pathways, DNA fingerprint analysis was performed. Results: A total of 38 patients (10.1%) developed a wound infection, in 14 patients this happened to be a deep wound infection, in 24 patients a superficial one. Five sternal wound infections were associated with mediastinitis (1.3%). The occurrence of a wound infection overall resulted in prolonged hospitalization (29.4±24 vs. 11.9±6.9 days, P=0.001), but not in increased hospital mortality (4.4% vs. 3.9%). Obesity, diabetes mellitus and nasal carriage of Staphylococcus aureus proved to be independent risk factors with an odds ratio of 2.07, 2.26 and 2.28, respectively. In all but one of the sternal colonizations with S. aureus, DNA fingerprint analysis demonstrated an identical pattern of S. aureus from the patient's nose and sternum, indicating an endogenous infection pathway. Conclusions: The determination of the endogenous pathway for severe wound infection makes prevention possible by means of preoperative local S. aureus eradication.