Coagulase-negative staphylococcal sternal wound infections after open heart operations

Coagulase-negative staphylococci are commonly isolated from wounds of patients after median sternotomy; however, the epidemiology of these infections is poorly described and the morbidity, mortality, and cost of care remain undefined.

Retrospectively, we studied all patients with sternal wound infections attributable to coagulase-negative staphylococci after 22,180 open heart procedures performed at the Cleveland Clinic between January 1, 1988, and December 31, 1994 (84 months). In an assessment of potential risk factors for sternal wound infections caused by coagulase-negative staphylococci, 17 patients with coagulase-negative staphylococcal sternal wound infections were compared with 29 patients who underwent open heart operations without subsequent sternal wound infections, as well as with another 22 patients in whom sternal wound infections attributable to other pathogens developed.

A total of 436 sternal wound infections were identified (19 per 1,000 procedures), of which 100 (23%) were attributable to coagulase-negative staphylococci (4.5 per 1,000). Fifty-six percent of coagulase-negative staphylococcal sternal wound infections were superficial, 27% were deep, and 17% represented mediastinitis; 14% of patients had a concomitant secondary bloodstream infection. Ninety-two percent of coagulase-negative staphylococcal isolates were methicillin resistant. The mean interval from operation to onset of infection was 24 days (range, 4 to 388 days), and most patients had purulent discharge from the chest wound, fever, and leukocytosis. Adverse outcomes included reexploration (39%), flap operation (12%), and sternectomy (5%); 89% required parenteral antibiotics for a mean of 22 days. This resulted in 2,600 additional hospital days, with an average additional direct cost per case of $20,000. In both case-control studies, insulin-dependent diabetes mellitus was the only risk factor significantly associated with sternal wound infections attributable to coagulase-negative staphylococci (p value = 0.02 by two-tailed Fisher's exact test).

Sternal wound infections attributable to coagulase-negative staphylococci had a substantial impact on cardiothoracic surgery-related morbidity.