The Latest on Group B Strep in Newborns

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We talk a lot about infections in pediatrics.  Among the many reasons for this are (1) most infants and young children are basically healthy, and (2) most problems that do crop up are related to infection, in part to the lack of a complete immune system in our youngest patients.

Not infrequently, a germ that affects babies—even one we’ve known about for a while—becomes a top news story.  One of the more recent items involves research on group B strep, a common variety of bacteria.  Before we discuss the latest findings, let’s review the germ and talk about why we get concerned about it.

A Group B Strep Primer

Group B strep is short speak for a variety of Streptococcus agalactiae (S. agalactiae), which is a type of bacteria.  You may know someone who’s had strep throat, which is caused by a related germ known as group A strep (Streptococcus pyogenes).  Group B strep, on the other hand, tends to live in the genital tract and rectum of about one in four women, where it usually causes no symptoms. However, when a woman with the bacteria gives birth, it can pass to the baby.

Again, because a baby’s immune system is not equipped to deal with certain bacteria, they are more prone to infection.  The infection caused by Group B strep in newborns is potentially much more serious and can involve the blood, the lungs, and the lining of the brain known as the meninges. (An infection of the meninges is known as meningitis.)  Serious complications may result.

We’ve Come a Long Way in Preventing Infection

Despite our knowledge that group B strep causes problems in newborns and that the germ is sensitive to certain antibiotics, it used to be that all we could do to suspect and treat the germ was look for clues—usually not very specific—in Mom during labor and Baby after delivery. Then, in the 1990s, things changed. At that point obstetricians began systematically testing pregnant women for group B strep.  If the germ was present, a woman in labor would receive antibiotics to treat it.  In some situations, the newborn was treated instead of or in addition to the mother.

This modern-day treatment leads us to the most recent news.  According to a recent article in JAMA Pediatrics, giving antibiotics to infected mothers has greatly reduced the amount of disease in newborns.  It used to be that 1.7 out of 1000 newborns would get group B strep disease. According to the most recent figure, it’s now 0.23 per 1000.

Other Challenges

This report is certainly great news. However, those encouraging numbers are only part of the story. They tell us we’re successful in reducing the incidence of early-onset group B strep—infection that shows up from birth to six days of age.  However, there is also something called late-onset group B strep which shows up from one week to three months of age.  Babies who get this are just as sick as those who get it in the newborn period, and may be even more likely to have meningitis.

According to the recent study, the numbers of late-onset group B strep have been fairly constant at 0.31 cases per 1000 babies.  What this means is that although it used to be much less common than the early-onset variety, and although it hasn’t increased in frequency, it’s now the most common cause of group B strep infection in young infants.

Because we know less about how babies get late-onset group B strep—some cases may originate from an infected mother, others from the community—we know less about how to prevent it.  Since treating Mom’s infection during labor doesn’t seem to be reducing the number of these cases, researchers are looking most closely at a vaccine to eliminate the germ before delivery.

While the era of group B strep vaccination may be a ways off, we clearly have come a long way in preventing disease in newborns and young infants due to the germ.  Mothers-to-be can help these efforts by saying “yes” to the very simple test done between 35 and 37 weeks’ gestation.  It’s also important that they receive preventive antibiotics in labor as directed by their obstetrician (21% who should have received antibiotics did not, according to the article, although there are likely many different reasons for this).  Finally, regardless of Mom’s group B strep status, families should always call their baby’s provider for any unusual signs that might indicate illness.

Stan Sack
Dr. Stan Sack has 29 years’ experience as a primary care pediatrician in Massachusetts and Florida. A medical writer since 2015, he enjoys blogging on topics that are on parents’ minds but are covered less often in books and on websites. He lives in the Florida Keys with his family and enjoys healthy cooking, fitness activities and singing in his spare time.

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