PREVENTION OF GROUP B STREPTOCOCCAL INFECTION

Abstract

Group B streptococci continue to be major perinatal pathogens, both for mothers and their infants, and are associated with significant morbidity, mortality, and its attendant cost to society. Approaches to prevention are directed toward either eliminating exposure to the organism or enhancing host resistance, that is, chemoprophylaxis and immunoprophylaxis. Intrapartum chemoprophylaxis has been shown to effectively interrupt vertical transmission of group B streptococci from the genitally colonized mother to the infant and to decrease the incidence of both maternal and early-onset neonatal group B streptococcal disease. To avoid unnecessarily exposing large numbers of colonized women to antibiotics, only those with defined risk factors should be selected for intrapartum chemoprophylaxis. This regimen is ampicillin given intravenously, 2 g initially at onset of labor or rupture of membranes, followed by 1 g every 4 hours until delivery. Risk factors include premature onset of labor or rupture of membranes before 37 weeks' gestation, rupture of membranes of more than 12 hours, intrapartum fever, group B streptococcal bacteriuria, or having previously delivered an infant with group B streptococcal disease. Detection of anogenital colonization is accomplished either by culture late in the second or early in the third trimester or by intrapartum group B streptococcal antigen testing of vaginal swabs from those previously culture-negative or not cultured. Although this approach combines the advantages of several proposed strategies, it will still miss those cases of group B streptococcal disease developing in the absence of discernible risk factors. Intrapartum prophylaxis does not prevent late-onset group B streptococcal disease. Prenatal and postnatal chemoprophylaxis have not been shown to be effective. Symptomatic infants born to mothers given chemoprophylaxis should be evaluated for neonatal sepsis and treated accordingly. This approach is also suggested for asymptomatic premature infants, those whose mothers have not received adequate prophylaxis or have previously delivered infants with group B streptococcal disease, and for twin siblings of infants developing group B streptococcal disease. Successful implementation of this approach may be limited by the availability and sensitivity of the rapid antigen test used. Immunoprophylaxis, and active immunization in particular, is the most promising method of preventing perinatal group B streptococcal disease in mothers and their infants, including late-onset disease. Immunization of pregnant women with type III polysaccharide vaccine has resulted in adequate provision of functional antibody to the infants born to responders.(ABSTRACT TRUNCATED AT 400 WORDS)