Font Size

Group B Strep Infection

What Is Group B Strep Infection?

  • Group B strep (GBS) causes serious infections in newborn infants and pregnant women.
  • Increasingly, group B strep also causes bloodstream infections and pneumonias in nonpregnant adults. Group B strep infections are treated with antibiotics.
  • To reduce the risk of infection in pregnant women and newborns, cultures are taken from pregnant women during late pregnancy, and intravenous antibiotics are given to those with positive cultures.
  • This practice has significantly reduced the number of serious infections in newborns and pregnant women.

What Causes Group B Strep Infection?

Group B strep infections are caused by bacteria from the species and genus Streptococcus agalactiae. Streptococci were divided into groups in 1933 by mixing the strains with antibodies that were produced in rabbits. Group B streptococci (GBS) have an outer cell wall that serves as a protective capsule which helps the organism resist the body's attempts to fight off the bacteria.

Group B strep may live harmlessly in the human body, which is called "colonization" or "carriage." During colonization, the organism lives on surfaces and membranes but does not invade tissues or organs. The most common site of colonization for group B strep is in the bowels. A significant percentage of women are colonized with group B strep in the vagina or cervix. Colonization is more common in people with diabetes and those who are sexually active.

An infection occurs when the bacteria invade the bloodstream, tissues, or organs. Newborns can become infected with group B strep as they pass through the birth canal if the mother carries the organism in her vagina. These infections are early-onset since they appear within the first week of life, often in the first hours after birth. In mothers colonized with group B strep, a small percentage of newborns will have early-onset infection. Since group B strep is carried in the bowels, the organism may also be spread if a person does not wash their hands properly after using the bathroom. Babies can also be infected this way, usually in the home, causing late-onset infections, which occur when the baby is 1 week to 3 months old.

Group B strep is not a cause of birth defects or autism and is not a sexually transmitted disease. Although babies may contract infections by contact with contaminated hands, washing with simple soap and water eliminates the organism. Group B strep is not contagious through coughing or sneezing.

Group B strep is a cause of infection in pregnant women. The organism may infect the bloodstream or the uterus. Older children and nonpregnant adults, especially older adults in nursing homes, may also get infections with group B strep.

Medically Reviewed by a Doctor on 11/21/2017

Must Read Articles Related to Group B Strep Infection

Abdominal Pain (Adults)
Abdominal Pain in Adults Abdominal pain in adults can range from a mild stomach ache to severe pain. Examples of causes of abdominal pain in adults include learn more >>
Antibiotics (Side Effects, List, Types)
Antibiotics Antibiotics are prescribed to individuals to cure disease by killing bacteria. There are over 100 antibiotics. The main classes of antibiotics include
learn more >>

Patient Comments & Reviews

The eMedicineHealth doctors ask about Group B Strep:

Group B Strep - Patient Experience

What was your experience with symptoms of strep?

Group B Strep Infection - Treatment

Please describe your treatment regimen for your group B strep infection?

Medical Dictionary