FAQ: Group B Streptococcus
Response by Dr. Anne Biringer, MD, Family Practice
Physician, Mount Sinai Hospital.
*Response by Dr. Allison McGeer, MD, FRCPC, Microbiologist, Department
of Microbiology, Mount Sinai Hospital.
» I am pregnant and my
doctor wants to check me for group B strep. Is this necessary?
Group B Streptococcus (Group B Strep or GBS) is a bacteria found
in the vagina and/or the lower intestine in up to 35% of all healthy
adult women. It does not generally cause problems for the mother,
however, during childbirth, GBS can be transmitted to the baby.
Newborns exposed to GBS may develop infections which include pneumonia,
sepsis (infection of the blood) or meningitis (infection of fluid
lining the brain.) Very few (1-2%) babies exposed to GBS become
ill, however, any infection in a newborn can be serious. A small
percentage of infants with GBS infection may be at risk for permanent
handicaps or even death.
Research has shown that giving the mother intravenous antibiotics
during labour can reduce the frequency of GBS infection in the
baby. Giving oral antibiotics to the mother in pregnancy is not
as effective.
» When should the test
for group B strep be performed?
There are two recommended approaches to the GBS
problem.
- Cultures for GBS are taken from all pregnant
women at 35 to 37 weeks of pregnancy. The test is a vaginal
and rectal swab which you or your doctor can perform. All women
who test positive for GBS are then given intravenous antibiotics
in labour (usually ampicillin but clindamycin if you are allergic
to penicillin). The antibiotics are most effective if they are
in your system for at least four hours before the baby is born.
- Another approach is not to screen mothers
with a swab but to give the intravenous antibiotics to all labouring
women who have a high risk situation for GBS infection in the
baby.
These high risk situations include:
- premature labour (before 37 weeks),
- prolonged rupture of the membranes (waters
broke more than 18 hours ago),
- fever in the mother during labour
- women who have had other newborns with GBS
infection
- GBS infection in the urine.
» If I have group
B strep, will my baby need to be tested?
If the mother received antibiotics at least 4 hours before delivery,
most newborns do not need to have tests to check for GBS. There
are situations when the baby may need blood tests to check for
infection or even intravenous antibiotics (usually given as a
precaution).
» Can group B strep
hurt my baby?
Although group B strep can cause significant illness in babies
and no treatment method can guarantee that a baby will not become
ill, giving preventive antibiotics as recommended in the above
protocols can greatly reduce the risk of GBS infection in the
baby immediately after birth or during the first week of life.
It is important that you discuss your individual situation with
your own doctor.
» What about Group B
Strep in adults that are not pregnant?*
Group B streptococcus is a bacterium which grows
normally in the bowels (and stool) of people. At any given time,
about 25% of people have a group B streptococcus in their bowel
at high enough concentrations for us to detect. Group B streptococcus
rarely causes infection in healthy people.
Infections due to group B streptococcus are
associated with older age, seriously compromised immune systems,
and problems with the bowel or bladder which make it easier for
these bacteria to invade deeper into the body. For instance, bladder
catheters allow bacteria to grow in the urine and cause infection
more easily. Bowel problems such as diverticular disease, cancer,
or inflammatory bowel disease make it easier for the bacteria
to invade damaged parts of the bowel wall and cause serious infections
such as bacteremia.
Group B streptococcal infection is not transmitted
from person to person, and you do not have to worry about contact
with an infected person.
For medical readers, there is a good review of
the epidemiology (frequency, risk factors for) infections due
to group B streptococci in the New England Journal of Medicine
1993, volume 328, pages 1807-1811, first author Dr. M Farley.
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