Staphylococcus epidermidis: an increasing cause of infection in patients with granulocytopenia

Staphylococcus epidermidis, a major component of the skin flora, is usually considered a contaminant when recovered from diagnostic cultures. Since 1974 infections caused by gram-negative bacilli and S. aureus occurring among patients with granulocytopenic cancer have remained constant; infections due to S. epidermidis occurring before 1977 at a rate of 2.0 per 1000 days of hospitalization of patients with acute leukemia, increased to 14.6 per 1000 days in 1979. All S. epidermidis infections before 1977 originated from skin sites; since 1977 the respiratory tract and alimentary canal have become the predominant sites of origin. Predisposing factors for infection were profound granulocytopenia (less than 100/microL), a diagnosis of acute leukemia, and an oral nonabsorbable antibiotic regimen lacking vancomycin. The increased incidence of infection was not related to a nosocomial source or the more frequent use of long-term indwelling catheters. Methicillin resistance among isolates was common (40%). Intravenous vancomycin therapy provided the best therapeutic results. Diagnostic cultures positive for S. epidermidis in the setting of infection and profound granulocytopenia warrant appropriate antibiotic therapy.