A Hospital-wide Outbreak of Septicemia due to a Few Strains of Staphylococcus aureus

Abstract

During a 6-month period at Walter Reed Army Hospital the monthly attack rate of Staphylococcus aureus bacteremia increased to 3.8 ± 0.5 (mean ± SEM) from 2.5 ± 0.2 cases per 1,000 dispositions for the previous 48 months (P < 0.05). A predominant phage pattern, designated S, was found in 12 (39%) of 31 bacteremic isolates typed and another strain, Δ, was associated with four catheter-related infections. Two other strains also accounted for infections. Patients with isolates of the S phage pattern had a higher mortality (59%) than patients with non-S isolates (37%). Thirty-eight per cent of S. aureus carriers among hospital personnel harbored S or A strains. Limitation of intravascular devices, strict handwashing, and the use of gloves were associated with a significant decrease in the incidence of S. aureus bacteremia to 1.9 ± 0.5/1,000 dispositions over the next 6 months (P < 0.05). S and Δ strains were reduced to 20% of these isolates despite their persistence in 32% of staphylococcal carriers upon reculture of personnel. We conclude that S. aureus persists as an important pathogen in the hospitals, and that phage typing S. aureus isolates remains an important tool in hospital epidemiology. The presence of multiple S. aureus strains causing this outbreak and the extent of their dissemination among patients and personnel reported here emphasizes the need to reevaluate strategies of nosocomial staphylococcal control.