Group B streptococcal infection

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at September 6, 2016
StartDiseasesGroup B streptococcal infection

Group B streptococcus infection is also referred to as group B strep and group B streptococcal infection. This infection is most severe when it is contracted by newborns, who can develop group B strep disease. Older people can also develop life-threatening conditions as a result of group B strep infection, although it is rare.


Definition & Facts

People who are healthy typically have no problems from this bacterial infection. However, those who have existing medical conditions such as diabetes mellitus or who have a weakened immune system are at an increased risk of becoming ill from the infection.

Group B strep is typically carried inside the lower intestine or in the genitourinary system. Babies can contract the infection while coming through the birth canal. In some cases, babies are infected while still in the womb. Adults who contract group B strep infections can be asymptomatic, though they also can go on to develop infections that can be life-threatening.

According to the United States Centers for Disease Control and Prevention (CDC), 1 out of 20 non-pregnant adults die from the infection. This prognosis is better for younger adults and those who do not have any pre-existing medical conditions. 

The CDC also states the risk of serious infection increases in non-pregnant women as age increases. In adults who are not pregnant, the infection occurs in 10 out of 100,000 people. However, this risk increases when adults are over age 65. In this age group, about 25 out of 100,000 people are reported to develop group B streptococcus. 

Symptoms & Complaints

The symptoms associated with group B streptococcus infection vary depending on who acquires it. Babies who contract this infection at birth can experience symptoms in two ways. Early onset group B strep infection occurs within one week after the birth of the baby. He or she may become lethargic, develop a fever, and refuse feedings.

Those who experience symptoms after a few months are said to have late onset group B strep infection. These babies have symptoms such as fever, irritability, problems feeding, and lethargy as well. They can also have difficulty breathing, develop pneumonia, and go into shock. Some babies also develop infections of the central nervous system like meningitis

Adults who carry the group B streptococcus infection typically have it in the urinary bladder, urinary system, lower intestines, rectum, throat, and vagina. Most adults do not get sick but those that do can develop dangerous blood infections known as sepsis.

The symptoms associated with sepsis include diminished alertness, chills, and fever. Infections of the lungs can also occur. The symptoms of lung infections such as pneumonia include chills, fever, chest pain, difficulty breathing and severe cough.

This bacteria can also cause infections of the skin that cause pus-filled lesions that are red and painful. The infection can even spread to the joints and bones, causing fever, chills and difficulty using the affected joint. 


Group B streptococcus is caused by a bacteria that lives within certain areas of the body. Experts believe this infection is present in up to 25 percent of pregnant women. This infection can live in a pregnant woman's uterus, urinary tract and placenta. Women who have this bacteria living inside their vaginal area can transmit the infection to their baby before birth. The risk of infection rises if the baby is born prematurely

Adults who carry the group B strep bacteria are at a higher risk of developing symptoms if they live in a nursing home or have an autoimmune disease. Those who are obese or who have had cancer are also at an increased risk of becoming sick from the bacteria. Group B streptococcus cannot be transmitted by saliva, water, food or through sexual contact. Most adults who carry the infection are unaware they have it. 

Diagnosis & Tests

In pregnant women, prenatal screening for group B strep bacteria is key to diagnosing and treating it. Obstetricians test for this bacteria between 35 and 37 weeks of pregnancy. During this test, the doctor takes a sample with a sterile cotton swab of the vagina. The sample is sent to a laboratory for testing. If it comes back positive, group B strep bacteria is present. It is important to note that a positive result does not mean the baby will be born infected with the bacteria. 

If the bacteria goes undetected during pregnancy, babies can be infected during birth. Doctors who suspect group B strep infection will perform tests on the newborn and draw blood to check for signs of the bacteria. A sample of cerebrospinal fluid may also confirm the diagnosis of group B streptococcus. 

Treatment & Therapy

The treatment for group B strep depends on the severity of illness and the age and health of the patient. Babies who are positive for the bacteria will receive treatment to help keep them stable. This often includes IV fluids, oxygen therapy, and intravenous antibiotics. Adults who have group B strep generally also receive antibiotics to treat the infection.

When this infection is discovered during pregnancy, doctors often prescribe antibiotics such as cephalexin or penicillin. In most adult cases, antibiotics are enough to stop the bacteria from causing serious problems.

In those who go on to develop complications such as pneumonia, bone infection, or sepsis, hospitalization will likely be required. Doctors will typically prescribe antibiotics and pain medications to manage severe symptoms. In severe cases, surgery could be required to stop the spread of infection. 

Prevention & Prophylaxis

Pregnant women who receive treatment during pregnancy typically have a favorable outcome for themselves and the baby. Early detection and treatment also reduces the chance of newborn infections.

The treatment among pregnant women with this infection is a short course of antibiotics. If the infection is under control during labor and delivery, the baby typically does not contract the infection. 

The key to keeping group B strep infections at a minimum is early detection. This is the best way to prevent the spread of the infection to babies during the birth process.