Group B streptococcal infection pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rim Halaby, M.D. [2]

Overview

The gastrointestinal tract serves as the primary reservoir for Group B Streptococcus (GBS) and is the likely source of vaginal colonization. Early-onset neonatal infections are acquired vertically through exposure to GBS from the vagina of a colonized woman. GBS is characterized by its ability to adhere to epithelial surfaces, such as the vagina, placental membranes, blood brain barrier, and respiratory tract. GBS can penetrate the host cell barriers and evade the host's immune response. The polysaccharide antiphagocytic capsule is this bacterium's main virulence factor.

Pathophysiology

Pathogenesis

GBS is characterized by its ability to adhere to epithelial surfaces, particularly the vaginal mucosa where the pH is low. The types of epithelium to which GBS adheres to are:

The series of events that explain the pathogenesis of GBS infection can be summarized as follows:[1]

Virulence Factors

The polysaccharide antiphagocytic capsule is this bacterium's main virulence factor.

Other key virulence factors include:[1]

Transmission

GBS in Pregnancy

The gastrointestinal tract serves as the primary reservoir for GBS and is the likely source of vaginal colonization.[2]

GBS in Neonates

Early-onset infections are acquired vertically through exposure to GBS from the vagina of a colonized woman. Neonatal infection occurs primarily when GBS ascends from the vagina to the amniotic fluid after onset of labor or rupture of membranes, although GBS also can invade through intact membranes. GBS can be aspirated into the fetal lungs, which in turn can lead to bacteremia. Infants also can become infected with GBS during passage through the birth canal; infants who are exposed to the organism through this route can become colonized at mucus membrane sites in the gastrointestinal or respiratory tracts, but these colonized infants most commonly remain healthy.[2]

References

  1. 1.0 1.1 Doran KS, Nizet V (2004). "Molecular pathogenesis of neonatal group B streptococcal infection: no longer in its infancy". Mol Microbiol. 54 (1): 23–31. doi:10.1111/j.1365-2958.2004.04266.x. PMID 15458402.
  2. 2.0 2.1 Verani J.R., McGee L, and Schrag S.J. Prevention of Perinatal Group B Streptococcal Disease. Revised Guidelines from CDC, 2010.CDC.gov

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