Elsevier

The Lancet

Volume 353, Issue 9146, 2 January 1999, Pages 51-56
The Lancet

Seminar
Group B streptococcus

https://doi.org/10.1016/S0140-6736(98)07128-1Get rights and content

Summary

During the 1990s the focus of group B streptococcus (GBS) disease research has shifted to prevention. Increased use of intrapartum antimicrobial prophylaxis in North America and Australia has led to substantial declines in perinatal disease. Vaccine development (initiated two decades earlier) has yielded results—for example, polysaccharide-protein conjugate vaccines given to women of reproductive age proved to be highly immunogenic and well tolerated. Also economic evaluations have assessed the cost-effectiveness of prevention strategies in different populations. Although GBS has traditionally been considered a perinatal pathogen, the burden of invasive GBS disease among nonpregnant adults has been measured. Adverse outcomes of pregnancy attributable to GBS were addressed through a multicentre study which confirmed the important role of heavy colonisation with GBS in preterm low-birthweight deliveries. Finally, the pathogen itself has continued to evolve: new capsular serotypes described in the past decade are now causing an important proportion of clinical infections.

Section snippets

Perinatal disease burden

Many adults are colonised with GBS in the genital and gastrointestinal tracts but remain free of symptoms. However, women colonised with GBS during pregnancy are at increased risk of premature delivery1 and perinatal transmission of the organism. Pregnancy-associated GBS disease is most often manifest during labour or within the first few days of an infant's life; it can affect the woman or her baby or both. Ascending spread leads to amniotic infection, which can result in maternal sepsis and,

Antimicrobial prophylaxis

The intravenous or intramuscular injection of antimicrobial agents after the onset of labour or rupture of the membranes is highly effective in reducing neonatal colonisation with GBS.4 Several clinical trials have demonstrated the efficacy of intrapartum antimicrobial prophylaxis in selected women (ie, GBS colonised, with or without obstetric complications such as preterm labour or rupture of the membranes, or prolonged rupture of the membranes) against laboratory-confirmed, early-onset GBS

Prematurity and GBS

The relation between GBS and prematurity is complex. The incidence of invasive disease (ie, sepsis and meningitis) is higher among preterm infants than among those born at term, although 74% of early-onset GBS and 56% of late-onset cases occur in full-term infants. Antibody transport across the placenta is reduced early in gestation. Preterm infants born to colonised mothers may have a higher risk of disease because lower amounts of protective maternal antibodies were transported across the

Disease in non-pregnant adults

Population-based surveillance in North America has demonstrated that most cases of invasive GBS disease, defined as isolation of GBS from a normally sterile site, occur among non-pregnant adults, although rates of invasive GBS disease are highest among infants. Among adults, incidence increases with age. Non-pregnant adults manifest sepsis, pneumonia, soft-tissue infections such as cellulitis and arthritis, and urinary-tract infections complicated by bacteraemia.23 Case-fatality rates for

GBS in non-industrialised countries

The apparent lack of significant clinical disease due to GBS in less developed countries is puzzling. Birth practices differ substantially around the world, and home births and less invasive procedures during hospital births might limit the risk of GBS sepsis in the newborn. However, detection of early-onset infections may be obscured by the large proportion of deliveries that take place outside health centres and the probability that infants who develop GBS sepsis on the day of birth will not

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