Bacteria in the Vag! Oh my!

One of the standard tests during pregnancy is for colonization of Group B Streptococcus (GBS) in your vagina. This is a common bacteria that colonizes the colon and vagina in about 25% of all women (and men also, for that matter, minus the vagina part). GBS does not make adults sick, but can be harmful to a baby. A woman who is positive for GBS has about a 1/200 chance of passing the bacteria on to her baby. The risk is very, very low, that the bacteria will affect the baby. However, the risks of GBS infection in the infant are scary enough that it is something to be worried about. There is a good chance of sepsis, pneumonia or meningitis if the baby does become infected and GBS remains a leading cause of infant mortality. The baby is especially at risk if it is born premature. Thus, all pregnant women are tested for GBS colonization between 35 and 37 weeks of gestastion and if a woman turns out to be positive, it is recommended that she be treated with intravenous antibiotics (usually penicillin) at the very start of her labor and every 4 hours following, until the baby is delivered. (This basic info can be found at the American Pregnancy Association website and the American Congress of Obstetricians and Gynecologists (AGOG) website)

Here is where the problem is. The recommendation to flood a pregnant women with antibiotics during labor is controversial, even among ACOG members. The high doses of penicillin necessary to kill the GBS has the effect of killing off all of the gut flora in the mother and in the newborn infant. Much of the infant's immune system is mediated by the gut flora that he/she is inocculated with during the descent through the birth canal. If this immune system is destroyed by high doses of antibiotics, it leaves the infant susceptible to antibiotic resistant strains of E. Coli and other nasty things. A recent study in one hospital noted that between 2004 and 2008 the screening of GBS colonization increased from ~10% to 65% and the use of intravenous antibiotic treatment increased from 40% to 90%. Although the rates of early-onset sepsis because of GBS decreased from 45.4% to 20%, the rates of sepsis caused by antibiotic resistant E. Coli increased from 40.9% to 70% (Lin et al., Pediatrics and Neonatology, 2011). The incidence of infant mortality due to early onset infections remained the same, even though antibiotic prophylaxis increased dramatically. 

There are also problems with the overuse of antibiotics not just with pregnant women, but with society in general. In a recent commentary in Nature (Antibiotic overuse: Stop the killing of beneficial bacteria. August 24, 2011), the author wrote that,  

The average child in the United States and other developed countries has received 10–20 courses of antibiotics by the time he or she is 18 years old¹. In many respects, this is a life-saving development. The average US citizen born in 1940 was expected to live to the age of 63; a baby born today should reach 78, in part because of antibiotics. But the assumption that antibiotics are generally safe has fostered overuse and led to an increase in bacterial resistance to treatments.

Other, equally serious, long-term consequences of our love of antibiotics have received far less attention. Antibiotics kill the bacteria we do want, as well as those we don't. Early evidence from my lab and others hints that, sometimes, our friendly flora never fully recover. These long-term changes to the beneficial bacteria within people's bodies may even increase our susceptibility to infections and disease. Overuse of antibiotics could be fuelling the dramatic increase in conditions such as obesity, type 1 diabetes, inflammatory bowel disease, allergies and asthma, which have more than doubled in many populations

The blanket recommendation to treat 30% of all pregnant women with penicillin during labor could be causing permanent changes in gut flora, leading to problems we don't yet fully understand. Not to mention that if a baby is born by C-section, they are not exposed to the vaginal flora and miss out on this important step in the development of their immune systems. The author continues,

Consequently, we should reduce the use of antibiotics during pregnancy and childhood. Antibiotics — particularly penicillins — are now given routinely to between one-third and one-half of all women during pregnancy or nearing childbirth in the United States and other developed countries. Babies acquire their founding bacterial populations from their mothers while passing through the vagina at birth. So each generation — particularly the 30% or so of infants born via Caesarian⁹ — could be beginning life with a smaller endowment of ancient microbes than the last⁵.

I just had the results of my GBS test come back and I am negative! This is good because it means that I don't need to fight with my Obstetrician about hospital policies, and because my baby is lower risk for a scary infection. I believe that if I had turned out to be positive, I would have declined to receive the IV antibiotics.  The antibiotics may decrease the spread of GBS, but at what cost? These practices are currently being reviewed and researchers are working on developing a vaccine for GBS that would eliminate the need for mass antibiotic treatments. Until better treatments are found, I would encourage other pregnant ladies to read the literature and make their own informed decision on this issue.


update: I had a friend who made some great comments that I thought would be good to include in this post.

Friend: I am thankful that you aren't GBS+ But, although controversial, there is a significant risk for children born to mothers who are GBS+ who aren't treated. There is a colleague of ours (works on our floor)...who lost a child several months after birth because of a GBS infection (they were unaware of the GBS and therefore not treated). It can be a serious thing...and is very scary...especially if the end result is the significant illness and/or death of a child. While antibiotic treatment may not be the best treatment...it is the current medical standard and has saved lives. How many lives that have been saved and complications prevented is difficult to document because...thats just it...the infections and therefore resulting deaths and complications were prevented. There are some things (like epidurals) that are truly just in place to make the delivery go smoother for the mother and for the doc (if there are no complications)...part of the "business of being born". Not getting an epidural is not life threatening. Not preventing an infection can be life threatening...and life ending. 


My reply: I didn't want to dismiss the risks of GBS, just point out that the current policy of antibiotics for all GBS+ women is probably not the best treatment. The increase of prophylactic antibiotic treatment has reduced GBS infection, but has had no effect on reducing infant mortality (most likely because of the increase of antibiotic resistant bacterial infections that are ironically caused by the antibiotic treatment itself). If it had saved lives, we'd see a reduction in infant deaths right? The point is that antibiotic treatment isn't so harmless as to justify it being used as a precaution, just in case, in all cases. And may be unsustainable as a public health policy.

Its definetly scary, but it just doesn't seem like the antibiotics are working the way that it was hoped! The policy was just introduced in 1996, and the kinks are still being worked out. In the last few years there has been a move away from blanket antibiotic treatment. The most recent CDC guidelines just came out in 2010 and advocate identifying the highest risk patients for antibiotic treatment. The best solution is most likely a GBS vaccine that I mentioned above, but until then the only treatment for high-risk patients (i.e. preterm births, mothers with a fever/infection, early rupture of the membranes, a previous GBS+ baby) is antibiotics during labor. For low-risk mothers, other options do exist. Regardless, I am not  advocating a complete rejection of antibiotic prophylaxix.  I think this is an important issue for pregnant women to educate themselves about.   


Final Note. Please see a very recent article that goes over the controversy really well. I could send it to you if you ask me. P. Melin. "Neonatal group B streptococcal disease: from pathogenesis to preventive strategies". Clin Microbiol Infect 2011; 17: 1294–1303