β-Hemolytic streptococci of Lancefield group B have been causally linked to neonatal disease since 1938, but only in the last decade has the group B Streptococcus become the leading etiologic agent for bacteremia and/or meningitis occurring during the first two months of life. Neither the reasons for the emergence of this organism nor the shifts over the past 40 years in the prevalence of various bacteria responsible for neonatal infection has been adequately explained. However, the importance of the group B Streptococcus as a frequent cause of neonatal mortality and morbidity demands a thorough understanding of the epidemiology and pathogenesis, clinical features, diagnostic methods, and management of these infections by physicians caring for newborn infants.
The common occurrence of neonatal group B streptococcal septicemia and meningitis in several geographically distant centers since 1970 has allowed the relatively precise determination of attack rates for early onset type (≤5 days) infection. Reported attack rates have been surprisingly uniform, varying from 1.3/1,000 to 4.0/1,000 live births (Table 1). Because the attack rates for serious neonatal infections associated with Escherichia coli and other maternally acquired coliform organisms have been constant since 1960, the appearance of the group B Streptococcus resulted in an absolute increase in the incidence of neonatal bacterial disease during the past decade in many hospitals in this country.