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What is GBS infection?
Group B streptococcus is a bacteria also known as Streptococcus agalactiae. It’s best known as the most common cause of severe infections in the newborn. But recent studies have shown that it may also cause serious infections in certain adults.
Group B streptococcal infections affect one in 2,000 babies born every year in the UK and Ireland. About 340 babies a year will develop group B streptococcal infection within seven days of birth (early group B streptococcus disease).
Causes of GBS infection
The bacteria is found living harmlessly in the vaginal and gastrointestinal tracts of up to 50 per cent of healthy women (and in many men too). It may be passed on to a baby either while the baby is still in the womb or during delivery. Although about 50 per cent of babies born to mothers carrying group B streptococcus pick up the micro-organism, only about one to two per cent of these newborns then go on to develop severe group B streptococcal disease.
Group B streptococcal sepsis is most likely to develop when the baby is premature or if there has been prolonged rupture of the membranes, with many hours passing before the baby is born, or if the baby has no antibodies to group B streptococci.
In the last 30 years it’s been show to be a cause of serious infection in non-pregnant adults too. It’s extremely rare in healthy people and is almost always associated with underlying problems such as diabetes or cancer, or less often, problems with:
Heart and blood vessels
About five per cent of affected adults will eventually experience a second episode of group B streptococcal disease.
Symptoms of GBS infection
If a pregnant woman is carrying (or ‘colonised with’) group B streptococcus, there is a chance she could pass it to her unborn baby. Most babies will not be harmed and will simply carry the bacteria themselves, but it can cause:
Late miscarriage and complications
Group B streptococcal disease in newborns is divided into early and late disease. Early group B streptococcal neonatal sepsis appears within 24 hours of delivery (and up to seven days afterwards) and accounts for over 80 per cent of cases. Typically it causes signs of pneumonia (breathing problems) or, less often, meningitis. Most of these babies will make a full recovery.
Late group B streptococcal neonatal sepsis appears between one week and three months after birth, and is more likely to cause meningitis. One in ten infected babies will die of blood poisoning, pneumonia or meningitis, while one in five will be affected permanently by cerebral palsy, blindness, deafness or serious learning difficulties.
Once a baby has reached three months of age, group B streptococcal infection is extremely rare.
In vulnerable adults, group B streptococcus can cause a range of different infections at different sites in the body.
Treatment for GBS infection
Group B streptococcus can be grown in the laboratory, and vaginal swabs are often taken towards the end of pregnancy among women thought to be at risk, to check for the bacteria. Rapid (on the spot) tests are not routinely carried out, because results are not always reliable.
Antibiotic treatment for GBS
Pregnant women who test positive for group B streptococcal infection should have antibiotics during labour, given through the vein (IV), to stop them passing the infection to their baby. Ideally, these women should have IV antibiotics for at least four hours before their baby is born. Antibiotics are not useful until labour has started.
There are also recognised situations when a pregnant woman requires treatment because there is an increased chance that her baby will be exposed to group B streptococcus. These include when the mother's waters break early (before 37 weeks gestation), when labour starts early (again, before 37 weeks gestation) or when the waters break more than 18 to 24 hours before the mother gives birth.
Swabs are taken from the mother and baby in such cases and the baby given intravenous antibiotics until the results of the swabs are back. If the swabs from the baby are negative, then the antibiotics can be stopped. A woman who has already had a baby infected in the past, or who has a raised temperature during delivery is also at higher risk of passing it on to her baby.
Should all at-risk women be treated?
Some women prefer not to receive antibiotics if their risk is only slightly increased. Experts advise that the risk of infection in the baby must be balanced against the wishes and beliefs of the woman in labour and against her risk of an adverse reaction to the antibiotics. If a group B streptococcus carrying woman had a healthy baby in a previous pregnancy, she is unlikely to be at greater risk with following pregnancies.
Scientists are trying to develop a vaccine for group B streptococcus, but technical problems mean that it's likely to be some years before one is available.
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