Streptococcus agalactiae, known as Group B Streptococcus (GBS), is a common bacterium found in the vaginal and rectal areas of healthy adults. While widespread, GBS typically does not cause symptoms in carriers.
What is Group B Streptococcus?
Group B Streptococcus is a bacterium that is part of the normal bacterial flora for many healthy individuals. It most commonly colonizes the gastrointestinal and genitourinary tracts.
The presence of GBS in a person’s body, referred to as colonization, can be intermittent. Estimates suggest that GBS colonizes the vaginal and gastrointestinal tracts of approximately 15% to 40% of healthy women. While generally harmless to the carrier, its presence becomes relevant during pregnancy.
GBS and Pregnancy
GBS presents a concern during pregnancy due to the risk of transmission to the newborn. A pregnant individual carrying GBS can pass the bacteria to their baby during vaginal birth. Approximately 50% to 75% of newborns exposed to GBS during delivery become colonized, and a smaller percentage, about 1% to 2%, may develop an early-onset invasive disease.
Early-onset GBS disease manifests within the first week of life, often within the first 12 hours after birth. Symptoms can include difficulty breathing, such as grunting or noisy breathing, being unusually sleepy or unresponsive, poor feeding, and an unstable body temperature. This form of GBS disease can lead to serious infections in infants, most commonly sepsis (a bloodstream infection) and pneumonia (a lung infection), and less frequently, meningitis (an infection of the brain and spinal lining).
Late-onset GBS disease occurs from one week to several months after birth, typically between 7 days and 3 months of age. Symptoms for late-onset disease can include irritability with a high-pitched cry, a blank stare, or seizures. This form is often characterized by meningitis or sepsis.
GBS can also pose less common risks to the pregnant individual, such as chorioamnionitis, an infection of the amniotic fluid, membranes, and placenta. This infection can be associated with preterm birth and stillbirth. Additionally, GBS can cause postpartum infections, including endometritis, an infection of the uterine lining after delivery.
Screening and Management
Standard procedures are in place to identify GBS in pregnant individuals to prevent transmission to the newborn. Routine screening for GBS is recommended for all pregnant women. This screening is typically conducted between 35 and 37 weeks of gestation.
The screening method involves taking a swab from both the lower vagina and the rectal area. These samples are then sent to a laboratory for culture to determine if GBS is present. The purpose of this screening is to identify individuals who are GBS carriers, allowing for preventive measures to reduce the risk of GBS infection in the newborn.
If a pregnant individual tests positive for GBS, the primary management strategy is intrapartum antibiotic prophylaxis (IAP) administered during labor. Antibiotics, commonly penicillin or ampicillin, are given intravenously every four hours until delivery. This approach aims to temporarily reduce the amount of GBS bacteria in the birth canal, preventing the newborn from acquiring the infection during passage. Antibiotics are given during labor rather than earlier in pregnancy because GBS colonization can be intermittent, and treatment too early might allow the bacteria to reappear before birth.
Potential Health Consequences
If GBS is not adequately managed during labor and delivery, there can be serious health consequences. For newborns, the most severe outcomes include sepsis, pneumonia, and meningitis.
Survivors of GBS meningitis may face long-term effects. These can include developmental delays, cognitive impairments, hearing loss, and cerebral palsy. Approximately half of infants who survive GBS meningitis may experience some degree of long-term morbidity. For the birthing parent, unmanaged GBS can lead to postpartum infections, such as endometritis. The emphasis on universal screening and appropriate treatment during labor significantly reduces these risks.