Invasive Group B Streptococcal Disease in Adults. A Population-based Study in Metropolitan Atlanta

Objective: To define the incidence and clinical spectrum of group B streptococcus infection in adults. To characterize groups at increased risk for infection.

Design: Retrospective population-based surveillance of group B streptococcus infections occurring in adults. Patients were identified by review of microbiology records at all surveillance area hospital laboratories. Demographic and clinical data were abstracted from patient medical records.

Setting: Metropolitan Atlanta, Ga, 1982 through 1983.

Patients: We identified 70 adult patients with invasive group B streptococcus infections; 14 infections occurred in pregnant women and 56 in nonpregnant adults.

Results: The annual incidence of group B streptococcus infection in men and nonpregnant women was 2.4 cases per 100,000 population. Incidence increased with age and was higher in blacks than in whites. The case-fatality rate was 32%. Group B streptococcus was most often isolated from blood (71%) and soft tissue (16%). Common clinical presentations included skin and soft-tissue infection (36%), bacteremia without focus (34%), pneumonia (11%), arthritis (9%), and endocarditis (9%). Compared with the general population's risk of infection, the risk of infection in persons with diabetes mellitus was increased 10.5-fold (95% confidence interval [CI], 7.8 to 14.4); in persons with cancer, it was increased 16.4-fold (95% CI, 11.5 to 23.3).

Conclusions: Group B streptococcus infections cause serious disease in adults as well as in neonates, providing an additional rationale for vaccine development. Determining the incidence of adult disease and groups at greatest risk will help in focusing prevention efforts.