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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 Streptoccus. 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 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 Streptoccus 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.
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.
Protecting the newborn
Since the introduction of antibiotic prophylaxis for carriers of the bacteria and those at risk in the 1990s, rate of this infection among newborns has fallen quite substantially.
The most effective way to protect the newborn against this infection is to give antibiotics to a known carrier of the bacteria during labour. This is a strategy that prevents transmission of the bacteria to the baby in 95% of cases. Penicillin is very effective but for those women who are allergic to this antibiotic, equally effective alternatives are available.
Increased risk
There are groups of women whose babies are particularly at risk of developing early-onset disease. For these women, antibiotic prophylaxis is imperative. The groups are:
Ø Where there has been prolonged rupture of membranes. This is generally defines as an interval of more than 18 hours between membrane rupture and delivery
Ø Preterm labour; that is before 37 weeks of gestation
Ø Raised temperature of 38˚C or above during labour.
Ø Previous infant with early onset GBS infection.
Antibiotics Regime
Antibiotics are given intravenously (i/v)as soon as the woman is in established labour and 4 hourly thereafter until delivery. Number of administrations of the drug will therefore depend on the duration of labour.
Penicillin is usually used with Clindamycin being the alternative where a woman is allergic to Penicillin. Clindamycin is administered 8 hourly. There are a number of other effective alternatives.
Caesarean Section
The use of antibiotics specifically targeting GBS appears to be of little or no value when delivery is by an elective caesarean section.
Group A Streptococcal Disease
This is mentioned briefly here for clarity and to make the distinction between this and its cousin discussed above.
Group A streptococcus, also known as Streptococcus pyogenes is the bacteria that causes what is generally known as Streptococcal disease. It is usually a disease of childhood and presents as acute sore-throat (pharyngitis). This may then be accompanied by a generalized rash mainly in the upper part of the body. It is then called ‘Scarlet Fever’. This infection has no relationship to Group B streptococcal infection.
Exposure of a pregnant woman to a patient with Scarlet Fever poses no direct risk to the unborn baby.
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