Invasive group B streptococcal (GBS) infection is a major health problem among infants and adults. The formulation of GBS vaccines depends on knowledge of the GBS serotype distribution. Serotype V GBS infection appears to have recently emerged, suggesting that the serotype distribution changes over time. GBS isolates from 210 pediatric patients, 23 pregnant women, and 314 nonpregnant adults with invasive infection in Maryland were studied. The predominant serotypes from infants with early-onset disease were as follows: serotype III, 38% of isolates; serotype Ia, 36%; serotype V, 13%; and serotype II, 11%. Although the majority (60%) of isolates among infants with late-onset infection were serotype III, serotype Ia (23%) was also common. The predominant serotype among isolates from nonpregnant adult patients was serotype V, accounting for 29% of the isolates. The serotype distribution differs between pediatric patients and adults and is changing over time. The inclusion of a relatively small number of serotypes in a GBS vaccine could provide protection against the vast majority of isolates.

Infection by group B streptococcus (GBS) is an important cause of bacterial disease in neonates, pregnant women, and nonpregnant adults. Whereas serotypes Ia, Ib, II, III, and V are most commonly associated with colonization and disease in the United States, strains of other serotypes have been isolated from patients in Japan. By use of an inhibition ELISA, the serotypes of 73 vaginal colonizing GBS strains isolated from healthy pregnant Japanese women were investigated. Twenty-six (35.6%) were type VIII, 18 (24.7%) were type VI, and the remaining 29 were distributed among more traditional serotypes. Strains were also tested by immunoblot for the presence of GBS surface proteins. Fifty-three (72.6%) of the 73 strains expressed one or more laddering GBS proteins. These data show that type VI and VIII GBS strains are common vaginal isolates in pregnant Japanese women and that one or more laddering proteins are present in most GBS strains.