Group B Streptococcus

Group B streptococcus, or group B strep, is a bacterium that causes life- threatening infections in newborns. Group B strep can also cause disease in pregnant women, the elderly, and adults with other illnesses.
Many people carry group B strep bacteria in their bodies without developing infection or illness. However, the bacteria can become deadly to people with weakened immune systems.
Pregnant women can transmit group B strep to their newborns at birth. Group B strep is the most common cause of blood infections and meningitis in newborns.
Most cases of group B strep disease in newborns can be prevented by giving certain pregnant women antibiotics during labor.

What is group B streptococcus (group B strep)?

Group B streptococcus (group B strep) is a bacterium that causes life-threatening infections in newborn infants. Group B strep can also cause serious diseases in pregnant women, the elderly, and adults with other illnesses. The letter "B" refers to a classification of bacteria in the genus Streptococcus according to the makeup of the organism's cell wall.

What kinds of illnesses does group B strep cause?

In newborns, group B strep is the most common cause of sepsis (infection of the bloodstream) and meningitis (infection of the lining and fluid surrounding the brain) and a common cause of pneumonia. Group B strep disease in newborns usually occurs in the first week of life ("early- onset"). Babies can also get a slightly less serious "late-onset" form of group B strep disease that develops a week to a few months after birth.

In adults, group B strep usually causes no symptoms. However, in rare cases, it can lead to serious bloodstream infections, urinary tract infections, skin infections, and pneumonia, especially in people with weakened immune systems and other health problems, such as diabetes.

How do people get infected with group B strep?

Group B strep bacteria are different from many other types of bacteria that can cause disease. People can be "colonized" with group B strep. This means that they carry the bacteria in their bodies but are not infected and do not become sick. Adults can carry the bacteria in the gastrointestinal tract, genital tract, or urinary tract. About 10% to 30% of pregnant women are colonized with group B strep in the genital tract.

Colonization with group B strep is usually harmless. The bacteria can become deadly, though, if something happens that allows them to invade the bloodstream. In adults, weakened immunity resulting from cancer treatment or a chronic illness can prompt an infection. More often, pregnant women who carry the bacteria can unknowingly transmit group B strep to their newborns at birth. Newborns can acquire early-onset group B strep disease either before or during delivery. The cause of late-onset disease in babies is not well understood.

How is group B strep infection diagnosed?

Group B strep infection is diagnosed by a laboratory test of blood or spinal fluid.

Who is at risk for group B strep infection?

Adults with illnesses that weaken the immune system, such as diabetes or cancer, are at risk of infection with group B strep.

An infant born to a woman who is carrying the bacteria can also be at risk. Some pregnant women are at more risk than others of having a baby who develops group B strep disease. A pregnant woman is at high risk if she:

Has already had a baby with group B strep infection
Has a urinary tract infection caused by group B strep
Becomes colonized with group B strep late in pregnancy
Develops a fever during labor
Has rupture of membranes 18 hours or more before delivery
Begins labor or has rupture of membranes before 37 weeks ("preterm")

What complications can result from group B strep infection?

Group B strep infection is fatal in about 20% of infected men and non-pregnant women and about 5% to 15% of infected newborns. Babies who survive can be left with speech, hearing, and vision problems as well as mental retardation.

What is the treatment for group B strep infection?

Group B strep infections in both newborns and adults are usually treated with antibiotics given intravenously (through a vein).

How common is group B strep infection?

Group B strep causes disease in about 18,000 people in the United States each year. Of these, about 8,000 are newborns. Group B strep is the most common cause of blood infections and meningitis in newborns and is a frequent cause of newborn pneumonia.

Is group B strep infection an emerging infectious disease?

Yes. Since 1970, group B strep infection has become the leading bacterial infection causing illness and death in newborns in the United States. Cases in adults are also on the rise. The number of adult infections nearly doubled during the 1980s and continues to increase.

How can group B strep infection be prevented?

Most cases of group B strep infection in newborns can be prevented by giving certain pregnant women antibiotics during labor. Antibiotic treatment before labor does not prevent group B strep infection in newborns.

Any pregnant woman who has already had a baby with group B strep infection or who has a urinary tract infection caused by group B strep should be given antibiotics during labor. Pregnant women who are colonized with group B strep should be offered antibiotics at the time of labor or rupture of the membranes. Colonization with group B strep can be detected late in pregnancy (35-37 weeks' gestation) by a special test of secretions from the vagina and rectum.

Unfortunately, some babies still get group B strep infection despite testing and antibiotic treatment. Vaccines to prevent group B strep infection are being developed.

This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health-care provider. If you have questions about the disease described above, consult a health-care provider.