Bacteremia with Streptococcus pneumoniae. Implications for therapy and prevention. Franklin County Pneumonia Study Group

OBJECTIVE: To determine the incidence and mortality rates of patients with bacteremic infections with Streptococcus pneumoniae, and to determine the serotypes and antimicrobial susceptibilities of the pneumococcal isolates. DESIGN: Prospective case ascertainment and procurement of S pneumoniae isolates between January 1991 and April 1994. SETTING: Ten adult care hospitals in Franklin County, Ohio. PATIENTS: Patients (N = 590) in whom S pneumoniae was isolated from blood cultures. MEASUREMENTS: Demographic data from patients with pneumococcal bacteremia were obtained by chart review. Pneumococcal serotyping and antimicrobial susceptibility testing were performed on 499 bacteremic isolates. RESULTS: Among residents of Franklin County, the annual incidence of pneumococcal bacteremia was higher in patients at least 65 years old (83.0 per 100,000 population) compared with younger adults (9.6 per 100,000 population) (odds ratio OR, 8.74; 95% confidence interval CI, 7.19 to 10.62) and more common among African Americans than whites (OR, 1.36; 95% CI, 1.06 to 1.75). The relative risk of pneumococcal bacteremia among persons infected with the human immunodeficiency virus was 41.8 times (CI, 19.0 to 92.0) that of county residents 18 to 64 years of age. The overall mortality rate was 19% and was age-dependent, reaching 38% in patients at least 85 years old. The distribution of pneumococcal serotypes causing bacteremia was remarkably consistent over time. The incidence of drug-resistant strains increased during the study period; by 1994 14% were resistant to penicillin, 12% to ceftazidime, and 24% to trimethoprim-sulfamethoxazole. The resistant strains included several serotypes of S pneumoniae. Most serotypes (89.8%) of S pneumoniae causing bacteremia are contained in the pneumococcal vaccine. CONCLUSIONS: Increased use of pneumococcal vaccine and recognition of antimicrobial resistance patterns may assist physicians in treating patients with S pneumoniae bacteremia. Educational programs to discourage unnecessary antimicrobial drug use should be developed for patients and physicians.