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Group B Streptococcus (GBS)

Elvis Elvis

Group B Streptococcus (GBS) has been present since the beginning of time. It was not until the 1970s that doctors became aware that it was one of the leading causes of death in newborn babies. Initially 20-50% of infected babies died.

All of us are familiar with the “strep throat”. Unfortunately most of us that go to the doctor for penicillin for sore throats turn out to have one of the many cold viruses for which we still have no cure. If we are in the 5-10% that really do have a strep throat than we really can benefit from penicillin. Untreated strep throat in children may even lead to rheumatic heart disease.

Most strep infections in humans are Group A Streptococcus. They usually cause severe upper respiratory infections, pneumonia, or skin infections. If untreated, they can even lead to death. Group B Streptococcus (GBS) on the other hand seldom causes serious infections in adults. GBS however is deadly for newborns. Prior to our current prevention strategy over 6000 newborns were affected each year in the US. One or two infants out of every 1000 born developed a serious infection. With our new preventive strategy only 1500 cases per year develop and there were only 110 deaths in the nation last year in newborns do to this deadly disease. This amounts to a 70% decrease.

Many modern bacteria have developed resistance to multiple antibiotics. Luckily GBS has remained 100% sensitive to plain, ordinary penicillin. Most babies are infected with GBS when passing through the birth canal. Even though GBS are in the birth canal they usually do not cause the mother any problems until delivery. The mother that has a 101 or higher temperature within the first 24 hours after delivery, usually turns out to have Group B Strep. It is usually easy to treat the mother but many infants die almost before we realize they are at risk.

Men and women often are carriers of GBS in their intestines and genital tracts. A pregnant woman’s carrier status can be intermittently positive throughout the pregnancy. We initially treated all GBS mothers early in pregnancy but found that it did nothing to decrease the death rate in newborns. They also would often test positive later on in the pregnancy. The only treatment found beneficial to the newborns was treating the carrier mothers when they first came in during early labor. This resulted in a 70% decrease of infected infants because, in addition to treating Mom, babies also receive penicillin across the placenta from their mothers. So when the baby went through the birth canal the mother had less GBS in the birth canal and the baby had penicillin already in its blood to fight any remaining bacteria. Most babies were found to have serious infections in less than one hour after delivery if the mother was untreated.

Group B Streptococcus (GBS)

Now all mothers are screened at 36 weeks gestation (about one month before delivery). If they test positive for Group B Strep., they are treated only when they are in active labor. Testing at 36 weeks involves wiping a soft Q-tip across the opening of the vagina and rectum. Special culture media is used to transport and identify these dangerous bacteria. GBS is usually only dangerous to newborn babies. Pregnant women only need to be treated for GBS in early pregnancy if it is causing a bladder or kidney infection.

Ninety percent of bladder and kidney infections of both pregnant and not pregnant women are usually caused by a bacteria called E. coli. However 5-10% of urinary tract infections are caused by GBS. Women with urinary tract GBS infections in pregnancy should be treated. They should also be given penicillin at the time they are in labor to decrease the risk to their infant. We no longer culture women in early pregnancy for GBS. We also don’t treat the women who are positive for GBS at 36 weeks until they are in labor.

Twenty to thirty percent of pregnant women are GBS carriers. Close to 100% of women are GBS carriers at some time during their lifetime. Women delivering prematurely (before the 36th week of pregnancy) or if the results of their GBS culture are unknown, are assumed to be positive and treated when they are in labor.

Ninety-eight percent of term (over 36 weeks gestation) infants survive if treated early for GBS. Only 70% of premature infants survive GBS if born before 33 weeks, even when treated. Bacterial infections in the mother, including GBS, account for 10 to 15% of all stillborns.

We are working to develop a reliable, rapid diagnostic slide test that could be used to test all pregnant patients when they are first in labor. We could then do away with testing at 36 weeks and not miss the patients that screen negative at 36 weeks but then are positive when they are in labor.

In the past we tried treating just high-risk groups or screening all pregnant patients and treating those women before they were in labor. This was not as successful as our current strategy. Screening all pregnant patients at 36 weeks and treating only the positive and high-risk patients resulted in additional 50% decrease in GBS disease in newborns. Women with previous babies having severe GBS disease should also be treated during all subsequent pregnancies. Women without ruptured membranes undergoing repeat cesarean sections do not need GBS prophylaxis.

Ideally if an effective vaccine is developed this will allow us to eliminate this disease as we have done with polio. Because of fear of lawsuits most large pharmaceutical companies have shown little interest in spending the millions necessary to develop these vaccines.