Perinatal Group B Streptococcus Infection

What is group B Streptococcus infection?

Group B Streptococcus (GBS) infection is caused by bacteria also known as Streptococcus agalactiae. Different parts of the human body can be affected. This bacterium is different from the more commonly known Streptococcus pyogenes that causes sore (strep) throat, scarlet fever, and impetigo.

Who gets GBS infection and what are the signs and symptoms of infection?

The majority of GBS infections are detected in pregnant women and their newborns. In pregnant women, the bacteria may cause urinary tract infection, infection of the womb and stillbirth. In newborns it may occur as two distinct syndromes, early- and late-onset disease, which are defined by how soon the illness occurs after birth. Early-onset disease (1 to 7 days after birth) is characterized by a blood stream infection, respiratory problems, pneumonia, shock and meningitis. Late-onset disease (7 days to several months after birth) is characterized by a blood stream infection and meningitis. It is estimated that in the United States each year a total of 7,500 invasive GBS infections occur in newborns. About 3/4 of the cases of GBS infection in infants are early-onset disease.

In individuals with underlying illnesses like cancer or diabetes, or other conditions that may alter the immune system, GBS may cause a variety of illnesses including blood stream infection, meningitis, pneumonia, inflammation of the lining of the heart, arthritis and skin infections.

How is GBS spread?

GBS are bacteria that live in the genitourinary and gastrointestinal tracts (vaginal and rectal area) of normal healthy individuals without causing any harm. Between 5 and 35% of pregnant women have GBS bacteria in one of these body sites. The transmission of GBS from mother to infant may occur shortly before or during delivery in early-onset disease. The risk of early-onset GBS disease is increased in pre-term (37 weeks gestation or less), a rupture of amniotic membranes more than 18 hours before delivery, maternal age of less than 20 years and the presence of fever during labor. In late-onset disease the route of transmission is less clear. GBS bacteria may also be spread from person-to-person via contaminated hands.

How soon do the symptoms appear?

The incubation period (the time from exposure to the bacteria to the time of onset of illness) for early-onset disease is less than 6 days. The incubation period for late-onset GBS is unknown, however symptoms usually occur between 1 week and 3 months of age.

What is the treatment for GBS infection?

When necessary, GBS infections may be treated with antibiotics.

How can GBS infection be prevented?

All pregnant women should be screened for the presence of GBS bacteria at 35 to 37 weeks in the pregnancy. Antibiotics may be given for those women who test positive for GBS bacteria. There are no special precautions when caring for infants with GBS infection other than good handwashing following contact with feces and urine.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.