Group B streptococcus

Group B streptococcus is a bacterium that can be found in both men and women, in the digestive tract or vagina. 

In most cases, its presence is harmless. 

In pregnant women and newborns, the bacteria can cause serious infections in the days or months following birth. It is the most common cause of severe infections in newborns.

What is it ?

Group B streptococcus or group B strep may also be referred to by its Latin name: Streptococcus agalactiae. 

It is a bacterium that can be found in both men and women, in the digestive tract or the vagina. In most cases, its presence is harmless. For example, the bacteria can be found in some women when a sample is taken from the vagina, without causing any symptoms: this is known as vaginal colonisation. 

Outside of pregnancy, group B streptococcus can also sometimes cause mild infections that are easily treated with standard antibiotics.  

Group B streptococcus is identified in the vagina of approximately 10-25% of women during pregnancy.

How does the baby become infected ? 

Transmission of the bacteria from mother to baby mainly occurs during delivery :

_When the baby passes through the vagina, through inhalation or ingestion of vaginal secretions colonised with group B streptococcus.
_When the waters break, through inhalation or ingestion of contaminated amniotic fluid.

If group B streptococcus is present in the mother at the time of delivery, the bacteria can infect the baby in one in two cases.

What are the consequences of infection ?

_ For the baby : If the mother is colonised and no preventive treatment is implemented, the baby has a one in two chance of becoming infected and approximately 1-2% of newborns will develop an infection.. 

Group B streptococcus can infect the baby very quickly after birth, within the first week of life and usually within the first 24 hours. The infection most often results in sepsis (general infection of the body) and respiratory distress (inability of the lungs to function properly).

Sometimes these symptoms are associated with inflammation of the membranes that surround the brain (meningitis).

Sometimes the infection occurs at a later stage. It occurs after the first week of life and, in most cases, before the second month. It usually results in meningitis with fever.

_ For the mother : After delivery, infection in the mother may be responsible for urinary tract infection,  
endometritis (infection of the lining of the uterus), sepsis or chorioamnionitis (infection of the placental tissue and amniotic fluid).

How and when should screening take place ?  

In pregnant women, it is recommended that routine screening for group B strep carriage is performed by taking a vaginal swab during the last month of pregnancy, ideally between weeks 34 and 38.

 If positive, this allows for preventive antibiotic therapy to be implemented at the time of delivery to limit the risk of infection for both mother and baby.

How can infection be prevented and/or treated ?

There is currently no available vaccine for group B streptococcus infections. There is also no way to avoid becoming a carrier of this bacteria.

Antibiotic treatment is offered in situations where there is a high risk of infection for the mother and baby after delivery : 

_ In the event of a positive result from a vaginal swab taken in late pregnancy
_ If there is a history of group B streptococcus infection in a previous pregnancy
_ If group B streptococcus is detected in the mother’s urine during pregnancy
_ If group B streptococcus is detected on a vaginal swab during pregnancy
_ If the baby is delivered before 37 weeks gestation
_ In the event of a fever during delivery
_ If the waters broke more than 18 hours before delivery

If the bacteria is isolated in the mother’s urine or vagina in early pregnancy, immediate treatment is not recommended, except in the case of symptoms that cause discomfort (itching, increased vaginal discharge). 

Indeed, treatment during pregnancy does not prevent the bacteria being present at the time of delivery. 

If screening has not been carried out, antibiotic treatment will only be given in other situations where there is a high risk of infection for both the mother and baby. 

Finally, if, despite preventive measures (antibiotic prophylaxis), an infection occurs, antibiotic treatment will be given to the baby or mother as appropriate.

What about breastfeeding ? 

Testing positive for group B streptococcus is not a contraindication to breastfeeding.

Ketterthill pregnancy booklet

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