Group B Streptococcus (Streptococcus agalactiae)
Group B Streptococcus (GBS) bacteria live in the throat, intestines, and vagina of at least 30% of the population and up to 40% of pregnant women without causing any illness. Most GBS infections occur in babies less than 3 months of age, with an incidence of about one in 1000 births. If the mother is a carrier, there is a 50% chance that her baby will be infected before or during birth.
Generally, mothers are immune to the types of GBS they carry and pass the antibodies to the baby during the last eight weeks of pregnancy. Consequently less than one per cent of full term babies who do carry GBS develop GBS meningitis or other severe GBS infection. Premature babies, especially those born before 32 weeks, do not share the mother's antibodies and are at much greater risk. GBS infections in newborns are serious, with a death rate of up to 20%, with many survivors sustaining permanent brain damage. GBS disease in infants occurs in two forms: early onset and late onset.
Early Onset GBS disease occurs in the first seven days after birth. It is a combination of pneumonia and septicemia (severe blood poisoning). Symptoms are often present at birth or develop within the first few hours. Usually severe pneumonia with marked respiratory distress is complicated by serious blood infection causing shock.
Risk factors include:
- Premature delivery
- Multiple births
- Premature rupture of the membranes ("water breaks") before labour begins
- GBS urinary tract infection in mother
- Fever in mother during labour
- History of newborn GBS infection
Late Onset GBS disease occurs between eight days and three months of age. It may consist of septicemia alone or in combination with meningitis, pneumonia, or joint infection.
No vaccine is yet available to prevent GBS in newborns. Antibiotics are usually given to women during labour if they are at high risk. This reduces the risk of Early Onset GBS but has no effect on the rate of Late Onset GBS.
Treatment of GBS infections is with antibiotics, given by vein, usually for two weeks or more.
Women whose babies become ill or die as a result of GBS infection need not feel guilty. GBS bacteria are one of a number of bacteria that normally live in our bodies. They occur naturally and are not a matter of hygiene or behaviour.