Contents
What is group B streptococcus, or Streptococcus agalactiae?
Le Group B streptococcus, GBS ou Streptococcus agalactiae, of its Latin name, is a bacterium which one finds in certain men and certain women, in the digestive tract or even in the vagina. This germ is often present in the body without necessarily causing symptoms.
A bacterium sometimes present in the flora of the vagina
Streptococcus B is found in the vaginal flora in at least 15% of women, asymptomatically. The Institut Pasteur specifies that this bacterium is found in 5 to 40% of women during pregnancy, ” according to the bacteriological techniques used and the populations studied “. But if the fact that it colonizes the vagina is usually without consequence for the pregnant woman, the presence of this bacteria can lead to infection of the baby during childbirth. So there is a protocol in place to reducee the risk of transmission.
Why test pregnant women for streptococcus B?
Although it is generally harmless in the woman who is a carrier, this germ can however be transmitted from mother to child, most often during childbirth, when passing through the vagina. Because the baby can inhaling or even ingesting vaginal secretions during childbirth, says the Institut Pasteur. An infection which is not without consequence in a newborn baby, because of its weak immune defenses.
That is why GBS screening is routinely performed in France, at the end of pregnancy, ideally between 34 and 38 weeks of amenorrhea, i.e. between 32 and 36 weeks of pregnancy.
In a document on “good clinical practices” published in 2001 and revised in 2006, the Haute Autorité de Santé (HAS) estimated that 10%, or at least 75 women per year in France are carriers of Streptococcus B in their vaginal flora.
Given that the consequences are important postpartum and for the newborn (a ” public health problem “ for HAS), and that prevention (i.e. the prescription of antibiotics during labor) reduces the risk of neonatal and maternal infection by more than three quarters, its screening at the end of pregnancy is fully justified, estimates the HAS.
Screening by vaginal swab
Unlike a smear from the cervix, screening for GBS is completely painless, since it involves collect some vaginal flora using a cotton swab, after placement of a speculum.
The sample taken is then cultured in the laboratory in order to reveal the presence or absence of Streptococcus B (GBS).
Note that this screening is recommended even if a cesarean section is scheduled or considered, in the event that the birth takes place earlier than expected. In the event of premature labor or premature rupture of membranes, the sample for screening for Sgb will be taken urgently, in order to avoid streptococcal B infection in the unborn baby.
What are the risks for the baby, for the mother?
Infection with Streptococcus B at birth can cause serious complications in a newborn baby. The medical community generally distinguishes two types of neonatal infections linked to Sgb : early infections, which occur in 80% of cases during the first 24 hours of a baby’s life, and late infections, which occur between the baby’s first week and third month.
A early infection by Streptococcus B in newborns is most often manifested by sepsis (or more precisely a bacteremia: presence of the bacteria in the blood) and a respiratory distress. While a late infection rather cause inflammation of the meninges, in this case a bacterial meningitis. The high fever is the main symptom.
Finally, for the young mother, streptococcus can colonize the urinary tract, and thus cause a urinary infection (or cystitis), or give rise to endometritis, that is, an infection of the endometrium that lines the uterus. In the most serious cases (and the rarest, fortunately), infection with Sgb can cause sepsis if the bacteria pass into the blood, ou chorio-amnionitis at the very end of pregnancy (infection of the placental tissues and amniotic fluid).
According to the Institut Pasteur, approximately 500 cases of neonatal infections invasive are identified in France every year, engendrant ebetween 30 and 60 deaths. Screening at the end of pregnancy, and the use of antibiotic treatment in the event of a positive sample, has made it possible to reduce the number of infections and the mortality of newborns.
Risk factors for transmitting streptococcus B to the baby
Note that there are risk factors for transmission group B streptococcus to the baby during childbirth, namely:
- early rupture of membranes;
- childbirth that lasts more than 18 hours;
- fever during childbirth;
- a history of maternal-fetal transmission of Sgb;
- the presence of Sgb in the urine.
What treatments to prevent infection with streptococcus B?
In pregnant women, systematic screening for streptococcus B is recommended between 34 and 38 SA. If the result is positive, and therefore the Sgb is present in the vaginal secretions, treatment with antibiotics (ß-lactam, i.e. penicillin or amoxicillin, or a macrolide in case of allergy) will be put in place at the time of childbirth, or from the rupture of the water bag in the absence of contractions. We talk about antibiotic prophylaxis, in other words preventive antibiotic treatment. Ideally, this treatment should be started at least 4 hours before the baby is born.
It should also be noted that in addition to a positive result in the screening test for Streptococcus B at the end of pregnancy, an antibiotic treatment is prescribed. in the following cases, even with a negative test :
- in the event of a history of Sgb infection during a previous pregnancy;
- in case of Sgb detected in urine during pregnancy;
- in case of Sgb detected in the vaginal flora during pregnancy;
- in the event of premature delivery (before 37 weeks, ie 8 and a half months);
- in case of unexplained fever during childbirth;
- when the rupture of the water bag is more than 18 hours old (in the event that childbirth has not yet been initiated).
In newborns, treatment for Streptococcus B infection is based on intravenous administration of an antibiotic beta-lactam type (amoxicillin) over 10 days to 3 weeks, depending on the symptoms and manifestations of the infection (meningitis, etc.).
Although it is rare for the bacteria to be transmitted to the baby, the baby will be closely monitored by the healthcare team, for early treatment in the event of symptoms of a Sgb infection.
Note that no vaccine is currently available against Streptococcus B infections.