Strep B has been the main cause of bacterial infection of the newborn in developed countries for decades. But how does this bacterium infect newborns?

Group B streptococcus or strep B is a type of bacteria of the Streptococcus genus. For decades it has been the main cause of bacterial infection of the newborn in developed countries. But how does this bacterium infect newborns? In this article, we explain it to you.

Strep B is part of the vaginal or rectal flora of a woman under normal conditions. In fact, the estimates are that about 25% of healthy adult women have this bacterium.

It is not a sexually transmitted disease, simply a colonization. Before advancing in the explanation, it is convenient to clarify these concepts:

Colonization refers to the proliferation of a microorganism somewhere. It does not necessarily cause harm.

The infection, on the other hand, refers to the damage, and eventual disease, that causes the proliferation of a microorganism.

In this way, the women carrying this bacterium, in general, do not present symptoms of any type. The danger of strep B is that, at the time of delivery, it can be transmitted to the fetus. If this happens, the bacteria will cause illness in the baby.

However, not all babies born to a strep mother get sick. However, there are circumstances that favor this happening. Among these possible conditions, it is found, for example, that labor occurs before the 37th week of pregnancy.

A urinary tract infection resulting from streptococcus during pregnancy or fever during childbirth are also circumstances that favor its transmission. Finally, the existence of a previous birth where the transmission of streptococcus to the baby had taken place, constitutes an advance that could happen again.

Prophylaxis of strep B transmission

For the prevention of complications it is necessary to administer antibiotics to the mother.

The Center for Disease Control and Prevention (CDC) recommends the evaluation of the presence of streptococcus in pregnant women. Pregnant women should take this test between weeks 35 and 37 of pregnancy. It consists of taking a sample from the outside of the vagina and the anus with a swab. That sample goes for analysis in the laboratory.

Some doctors do not do tests for strep B. Instead, they choose to treat all pregnant women at risk of transmitting streptococcus to the baby. The treatment consists in the administration of antibiotic intravenously during delivery. The antibiotic used is usually penicillin. In the case of allergic women, they take another medicine. When there is proof that the streptococcus is present in the vagina or in the anus of the woman, the test is positive.

It is also considered that colonized women are lifelong carriers. This means that the streptococcal colony never disappears. Taking antibiotics before delivery will not protect the baby from the streptococcus, as the colony multiplies rapidly. That is why they are administered just before delivery and intravenously. According to the consensus within the medical community, it is to provide it four hours before giving birth.

They get a very powerful dose that substantially and quickly reduces the number of bacteria. Thus, when the baby comes into contact with the area where the colony was located, there will not be enough bacteria to infect it. Later, they will reappear, but the baby will no longer be in contact with those bacteria.

Consequences of group B streptococcal infection

Although it is currently unlikely, it is possible for the newborn to develop a group B streptococcal infection. It may occur because the prophylaxis strategy has not been effective or due to malpractice. Streptococcal infection can develop early or late. The most common complications of the early form are sepsis, pneumonia and meningitis. It is possible that the newborn presents signs and symptoms a few hours after delivery.

The late form is less frequent than the early one. It can develop up to 3 months after delivery. The most common complication is meningitis. The late onset may also be due to contact of the baby with a streptococcal focus other than the birth canal.

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