Group B strep (streptococcus) is a common bacterium often carried in the intestines or lower genital tract. The bacterium is usually harmless in healthy adults. In newborns, however, it can cause a serious illness known as group B strep disease.
Group B strep can also cause dangerous infections in adults with certain chronic medical conditions, such as diabetes or liver disease. Older adults are at increased risk of illness due to group B strep, too.
If you're a healthy adult, there's nothing you need to do about group B strep. If you're pregnant, get a group B strep screening test during your third trimester. If you have group B strep, antibiotic treatment during labor can protect your baby.
Most babies born to women carrying group B strep are healthy. But the few who are infected by group B strep during labor can become critically ill.
In infants, illness caused by group B strep can be within six hours of birth (early onset) — or weeks or months after birth (late onset).
Signs and symptoms might include:
Many adults carry group B strep in their bodies — usually in the bowel, vagina, rectum, bladder or throat — and have no signs or symptoms.
In some cases, however, group B strep can cause a urinary tract infection or other more-serious infections. Signs and symptoms of infections that may be caused by group B strep include the following.
Urinary tract infection
Blood infection (bacteremia)
Skin or soft-tissue infection
Bone or joint infection
If you have signs or symptoms of group B strep infection — particularly if you're pregnant, you have a chronic medical condition or you're older than 65 — contact your doctor right away.
If you notice your infant has signs or symptoms of group B strep disease, contact your baby's doctor immediately.
Many healthy people carry group B strep bacteria in their bodies. You might carry the bacteria in your body for a short time — it can come and go — or you might always have it. Group B strep bacteria aren't sexually transmitted, and they're not spread through food or water. How the bacteria are spread to anyone other than newborns isn't known.
Group B strep can spread to a baby during a vaginal delivery if the baby is exposed to — or swallows — fluids containing group B strep.
An infant is at increased risk of developing group B strep disease if:
Adults age 65 and older are at increased risk of group B strep. You're also at increased risk of if you have a condition that impairs your immune system or other serious diseases, including the following:
Group B strep infection can lead to life-threatening disease in infants, including:
If you're pregnant, group B strep can cause the following:
If you're an older adult or you have a chronic health condition, group B strep bacteria can lead to any of the following conditions:
If you're pregnant, the American College of Obstetricians and Gynecologists recommends a group B strep screening during weeks 36 to 37 of pregnancy. Your doctor will take swab samples from your vagina and rectum and send them to a lab for testing.
A positive test indicates that you carry group B strep. It doesn't mean that you're ill or that your baby will be affected, but that you're at increased risk of passing the bacteria to your baby.
To prevent group B bacteria from spreading to your baby during labor or delivery, your doctor can give you an IV antibiotic — usually penicillin or a related drug — when labor begins.
If you're allergic to penicillin or related drugs, you might receive clindamycin or vancomycin as an alternative. Because the effectiveness of these alternatives is not well understood, your baby will be monitored for up to 48 hours.
Taking oral antibiotics ahead of time won't help because the bacteria can return before labor begins.
Antibiotic treatment during labor is also recommended if you:
Although it's not available yet, researchers are working on a group B strep vaccine that could help prevent group B strep infections in the future.
After you give birth, if your doctor suspects your baby has group B strep disease, a sample of your baby's blood or spinal fluid will be sent to a lab for evaluation.
If your baby appears ill, he or she might be given other tests, including:
For adults who are diagnosed with an infection, a blood test can determine if group B strep is the cause. Identifying the cause may be important for determining the appropriate treatment.
If your baby tests positive for group B strep, he or she will be given intravenous (IV) antibiotics. Depending on your baby's condition, he or she might need IV fluids, oxygen or other medications.
Antibiotics are effective treatment for group B strep infection in adults. The choice of antibiotic depends on the location and extent of the infection and your specific circumstances.
If you're pregnant and you develop complications due to group B strep, you'll be given oral antibiotics, usually penicillin, amoxicillin (Amoxil, Larotid) or cephalexin (Keflex). All are considered safe to take during pregnancy.
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