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Group B Haemolytic Streptococcal ‘Infection’ and Pregnancy

By Dr J Kabyemela, MD

One of the enduring  problems that plague medical science is the preponderance of unwieldy names and terms which make communication with everybody else that little bit more difficult.

What is in a name?

There is a group of bacteria known as Streptococcus. The name comes from the fact that the shape of each one is oval(coccus)  and they tend to appear in chains or strips (strepto). They are called ‘haemolytic’ or ‘hemolytic’ (USA) because when cultured in a laboratory dish, they will tend to cause the break-up of blood cells, a process called haemolysis.  

Streptococcal bacteria are divided in several groups including A, B, C, D, G and R. We shall only concern ourselves with Group B and (very briefly) A. So you know.

Group B Streptococcus (GBS)

The full name is Group B beta-hemolytic Streptococcus. It can be argued that the presence of these bacteria in the genital tract is not a legitimate infection. There is merit in this argument considering that at least a quarter (25%) and possibly up to a third of all adult women are believed to carry these bacteria in the vagina and it does them no harm at all.

The vaginal tract, like the oral cavity, is normally home to a variety of bacteria and that is not evidence of disease. It is normal. For some women, the bacteria in the vagina include Group B Streptococcus or GBS as is otherwise known. Except in a situation where the woman’s immune system is compromised, the presence of GBS would not be regarded as clinically significant and no treatment is required.

GBS only becomes significant for a woman when she becomes pregnant. There is, then, the risk of passing on the bacteria to her newborn at the time of delivery. Unlike the mother, the baby will be vulnerable and therefore at risk of infection which can be quite serious. The infection in the newborn could present early or late.

Early and Late GBS Infection

Early disease takes the form of blood poisoning (septicaemia) and there may be associated pneumonia and meningitis. In the vast majority, onset is within hours of birth but can be up to 7 days after.

The baby will present with irritability, lethargy, breathing difficulties and will soon turn blue (cyanosed). The progression of the disease is quite rapid and aggressive treatment is required as the disease is life-threatening and there are fatalities.

Late disease is usually in the form of  meningitis and could occur as late as three months after delivery. Roughly 20% of all GBS infections present late. Roughly half of these will occur to babies whose mothers are non-carriers of the bacteria.

GBS infection could also affect joints (septic arthritis), bones (osteomyelitis), the ear-canal (otitis media), the eye (conjunctivitis) and other parts of the body. These presentations are not common.

GBS Infection Prevention

In the United States and Canada, the recommendation is to do universal screening and offer antibiotic prophylaxis during labor to those women found to have a positive culture for GBS. A vaginal and rectal swab is taken for culture at 35-37 weeks of gestation. Now, there is a suggestion from some experts that a rapid test for GBS infection in labour is possible and desirable.

In the UK, there is no universal screening for this ‘infection’. The logic being that the screening is unlikely to be reliable since colonization of the vagina by GBS bacteria is known to be intermittent. It therefore follows that a woman could test negative at some point during pregnancy but actually have the bacteria a few days or weeks down the line. The results therefore carry the risk of being misleading.

For those who are already known to carry the bacteria, there appears to be little or no value in giving them antibiotics during pregnancy and before labour. This is because, even though antibiotics are very effective in eliminating the bacteria, effectiveness appears to be temporary and the bacteria is likely to be back just a few weeks afterwards.

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