Although all women are tested for group B streptococcus during pregnancy, current screening methods can leave some babies at risk for contracting an infection from the bacterium. But the new test, which UF researchers studied for several months as part of a clinical trial, allows health-care workers to quickly screen mothers during labor, improving the odds that babies will receive preventive care so they will not be infected during delivery.
"Without any intervention, (group B strep) is the most common cause of early-onset infection in newborns," said Rodney Edwards, M.D., a UF assistant professor of obstetrics and gynecology in the College of Medicine who led the clinical trial at UF, one of six sites to study the test. "It can cause sepsis, meningitis and pneumonia. The likelihood of dying if you are a newborn is 5 percent. (With meningitis) even if the baby makes it through the infection there is a chance of cerebral palsy and cognitive delay."
The new group B strep test, developed by the California-based company Cepheid, allows doctors to screen for the bacterium during labor. Currently, women are screened for the organism a few weeks before birth because it takes a few days to receive results from the lab. But because some women do not contract the organism until after they are tested, some babies are still at risk for infection.
The first clinical molecular diagnostic test the FDA has approved, the technology can be adapted to detect other infections such as avian flu and even the deadly bug methicillin-resistant Staphylococcus aureus, Cepheid officials say.
About one-quarter of women carry group B streptococcus in their bodies, according to the Centers for Disease Control and Prevention. The bacterium, typically found in the rectum and vaginal tract, causes few problems for adults, but in babies, whose immune systems can't fend off bacterial invaders as easily, it can be deadly. The germ differs from group A streptococcus, which causes strep throat.
Only one to two of every 1,000 babies born develop group B streptococcus infections within their first week of life, and most of the children who contract the bug do not develop problems. But of the babies who develop sepsis, meningitis, pneumonia or other complications from group B streptococcus, about 15 percent die, according to the American College of Obstetricians and Gynecologists.
Federal guidelines require doctors to screen all women for the organism between 35 and 37 weeks of pregnancy. Women who test positive are then treated with antibiotics during labor.
"The patients we worry about are the ones who go into labor before their culture is done," said Amy Murtha, an assistant professor of obstetrics and gynecology at Duke University, who was not involved with the clinical trial. "It would be helpful in those instances to have a rapid test to screen for group B strep."
Edwards said the Cepheid test takes about 75 minutes to yield an answer and can be performed by health-care workers in the hospital, instead of in a lab.
The test uses technology known as a polymerase chain reaction, meaning it can amplify a small sample of DNA from a vaginal swab to detect the virus. Unlike other tests using this technology, Cepheid's test does not require the sample to be separately prepared prior to running the test. A nurse can insert the patient's sample directly into the self-contained test. This is what makes it so easy, Edwards said.
UF nurses performed the test on women in labor during the clinical trial. Lab technicians also tried out the test to screen pregnant women prior to labor. At UF, about 240 women were screened with the Cepheid test, Edwards said.
"The test seems to perform quite well," Edwards said.