What Causes Group B Strep?

As the American College of Obstetricians and Gynecologists states, Group B streptococcus, also known as group B strep or GBS, is a common type of bacteria. In healthy adults, GBS usually does not cause any illness. In newborn babies, people with chronic medical conditions, and the elderly, however, group B strep can cause serious infections.

General Transmission

• According to the Mayo Clinic, group B strep is commonly found in the intestines or reproductive systems of both men and women. Many people carry GBS in their bodies without experiencing any symptoms. According to the American College of Obstetricians and Gynecologists, such people are said to be colonized. GBS is not a sexually transmitted disease; instead, it can spread whenever someone comes into contact with a substance containing the bacteria. (Since GBS is fairly common, this may occur quite easily.) As the Mayo Clinic explains, some people have group B strep in their body throughout their entire life, while others only harbor the bacteria for a limited period of time.

Pregnant Women

• According to the American College of Obstetricians and Gynecologists, GBS is found in 10 to 30 percent of pregnant women. While the cause of group B strep in pregnant women is no different than for other adults, pregnant women are singled out because they can pass group B strep to their babies during delivery. Women are routinely screened between 35 and 37 weeks of their pregnancy, with a simple swab test of the vagina and rectum.

Newborn Babies

• According to the American College of Obstetricians and Gynecologists, the cause of group B strep infection in a newborn is often vaginal delivery by a mother who has been colonized by GBS bacteria. Newborn babies can be infected with group B strep during a vaginal birth since GBS typically resides in a woman's vagina or rectum. This is why pregnant women are tested as part of their prenatal care, and are given antibiotics during the labor and delivery if they test positive, to ensure the newborn is not infected.

Non-Pregnant Adults

• According to the CDC, group B strep can also cause infections in people with weakened immune systems, such as the elderly and people with medical conditions like liver disease, cancer or diabetes. While these people pick up GBS bacteria in the same generally innocuous way as other adults, their immune system's inability to protect against normally harmless bacteria can lead to a group B strep infection.

Prevention

• There is currently no particular way to prevent GBS infection in adults. According to the CDC, standard infection control measures can reduce the likelihood of contracting group B strep bacteria; researchers are also attempting to develop a vaccine against the bacteria. To prevent group B strep infections in newborns, pregnant women should be tested for GBS between 35 and 37 weeks of pregnancy, according to the American College of Obstetricians and Gynecologists. Make sure to ask your practitioner for this test if they don't routinely perform it, so that antibiotics may be administered during delivery.