Touching Lives - December 2003
Countering the deadly threat of meningitis
Known as Group B Streptococcus (GBS), the bacteria live harmlessly in the intestines in around a third of all men and women. These bacteria are also found in the vagina of around a quarter of all women of childbearing age, although there will be no outward symptoms of their presence and they do no harm to the woman.
GBS only becomes dangerous during childbirth when the baby is exposed to the bacteria as it passes through the birth canal. The newborn baby appears to be much more susceptible to infection as its immature immune system may be unable to cope. Approximately one in every thousand babies will become ill and tragically about ten to 20 per cent of those will die.
Signs of GBS infection in newborn babies include poor feeding, abnormally high or low temperature, abnormal breathing, a blue tinge to the skin, grunting and lethargy. Babies who are thought to have a GBS infection need to be given antibiotics and must be taken to the doctor or hospital immediately. The good news is that with treatment the majority of babies who develop the infection have no long-term damage.
A minority of babies however will develop GBS meningitis. ^GBS meningitis can have devastating consequences, and up to a third of babies suffer long-term mental and/or physical disability^. These could be from mild learning disabilities to severe mental retardation, loss of sight, loss of hearing and epilepsy.
Action Medical Researchers Karen Oliver, Nicola Jones and Naiel Bisharat have been studying the DNA of GBS to see how bacteria evolve in certain conditions, and what the potential might be to develop a vaccine to guard against GBS infection. They have been using a molecular technique called Multilocus Sequence Typing (MLST), which analyses some of the genes of GBS. They have identified a strain of the bacteria called ST-17, which commonly causes serious infections.
The strain was only occasionally identified in the mothers but much more commonly found causing disease in the babies, suggesting that when a mother has this strain it is more likely to be passed to the baby. The team studied ST-17 to see if it was possible to work out what makes it more likely to cause disease in newborns. In future, ST-17 could become the focus of research into the development of a new test for GBS in pregnant women or in the development of a vaccine.
In addition, the Oxford team have developed a database detailing how frequently GBS occurs in pregnant women and how often GBS causes disease in babies. This provides a useful source of data for doctors, midwives and scientists in the UK on which sorts of patients will get GBS infection, how common GBS is in the UK, and details about pregnancies. Giving antibiotic injections to the mother during labour and birth can prevent GBS infection in newborn babies.
The Royal College of Obstetricians and Gynaecologists has recently published guidelines which outlined risk factors in mothers, which if present should prompt midwives to administer the antibiotics. It is hoped that cases of GBS in babies will be reduced as a result of these guidelines.
The aim for the future is to develop a vaccine for the bacteria, which can be given to pregnant women to protect their unborn baby. Although ST-17 does seem to be important, other strains of GBS also cause disease in babies and a vaccine would need to be active against most or all of these strains.
Estee Torok, a microbiologist at the John Radcliffe Hospital, gave birth to her son Ben six months ago and took part in the GBS study.
Estee explained to Touching Lives, “With my first child Oliver I had prolonged rupture of membranes, which is a risk factor for the transmission of GBS. When I became pregnant again I was offered the opportunity to be screened for GBS as part of the study. It was very reassuring to have a negative result, particularly as Ben developed a fever shortly after he was born. Fortunately, he was fine and the temperature settled after a few hours.
“In the UK guidelines have been developed to minimize the risk of transmission of GBS from mother to baby. They list what risk factors midwives should look out for so that the best care can be given to mother and baby. Not all people who carry GBS transmit it to their child and only a few babies develop septicaemia or meningitis.
“I have seen some babies who have had GBS meningitis and it can be a devastating disease. In one particular case, a baby was suffering with drowsiness, poor feeding and fits. Unfortunately, the diagnosis of GBS meningitis was delayed and the baby was severely brain damaged. If a vaccine could be developed in the future I think that would be very reassuring for mothers.”
Anne-Kirstine Nissen also took part in the study. She found out about a week before she was due to give birth to Adam that she had a positive GBS result.
“I wasn’t worried about having the bacteria at all. Your skin is covered in bacteria and as long as it doesn’t go inside the body then you are fine. Being a vet I knew that I would just be given large doses of antibiotics, probably comparable to what you would give a horse! You have to have top ups of antibiotics every four hours, but luckily I gave birth after eight hours so I only had two. Adam had a minor infection after the birth but there was no streptococcus found, so the antibiotic protection for the GBS had worked.
“I think that women should either be screened or precautions should be taken. So if the birth is taking longer than 12 hours, give the women the antibiotics or screen as part of the normal screening process. I had a friend in France whose baby had an infection and it was really devastating as the baby had to be taken to a different hospital and so she didn’t see him for four days. ^Luckily meningitis is quite rare — but any new developments that avoid this condition in the first place are really important^.”