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Mount Sinai Hospital is a University of Toronto patient care, teaching, and research centre.
Mount Sinai Hospital is a University of Toronto patient care, teaching, and research centre.

Frequently Asked Questions

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.

  1. 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.
  2. 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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