Group B beta-hemolytic streptococci, or Streptococcus agalactiae, are normal flora of the lower intestinal tract and female genital tract in up to 35 percent of women. Colonization of the vagina with group B streptococci typically is an indication of contamination from the rectum. In the woman, vaginal colonization with group B streptococci is usually asymptomatic. However, the presence of the bacterium in the female genital tract during the time of childbirth can lead to infection of the newborn.
Early-onset Disease
The bacterium that is colonized in the vagina at the time of birth can result in severe neonatal disease. The organism is acquired by the neonate in utero before delivery either through ruptured fetal membranes, or during passage through the colonized birth canal. Early-onset disease usually happens during the first week of life, with many infants becoming ill within 24 hours after birth. The disease presentation in the newborn with early-onset disease is characterized by signs and symptoms of bacteremia (bacteria in the blood) and pneumonia. Though all infants are susceptible, the attack rate and death rate is higher in preterm than in full-term infants.
Late-onset Disease
Late-onset disease from group B streptococci in the newborn usually becomes evident between one week and several months after birth, with an average time of about a month. More than half of infected newborns get infected from the birth canal of infected mothers; some cases are acquired from the mother or other caregiver. Meningitis is the predominate clinical disease associated with late-onset disease. Many children with late-onset meningitis end up with neurological complications. Other complications from group B streptococci in the newborn child include hearing loss, vision loss and mental retardation.
In the Mother
Group B streptococcal infections may also happen to the mother. Among the more serious complications are postpartum endometritis, post-cesarean wound infections and bacteremia, pre-term labor and sepsis.
Prevention
Given the severity of group B streptococcal infections in newborns, the Centers for Disease Control and Prevention–in conjunction with the American Academy of Pediatrics and the American College of Obstetrics and Gynecology–issued a protocol of antibiotic administration during labor and delivery. The use of penicillin during labor reduces the risk of neonatal infection by removing the colonized group B streptococci. In addition, a microbiological culture protocol was established testing the mother’s vagina and rectum at Weeks 35 and 37 of gestation. These protocols have decreased group B streptococcal infections in newborns dramatically.
