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Group B Streptococcus (GBS)

Discussion in 'Glossary and Definitions of Terms' started by _Josie, May 26, 2010.

  1. _Josie

    _Josie Well-Known Member

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    Group B Streptococcus (GBS) is the most common cause of life threatening infections in newborn babies in the UK. Without preventative medicine, GBS infects around 700 babies each year, of which around 75 will die and 40 survivors suffer long-term problems as a result (Group B Strep Support).

    GBS colonises the intestines and vagina of 20-30% of women, without symptoms or side-effects, however, GBS can cause infection, most commonly in babies, before, during or shortly after birth. Treating women carrying GBS during pregnancy does not eradicate colonisation or prevent re-colonisation, nor is there any evidence it reduces the incidence of GBS infection in newborn babies.

    Intrapartum antibiotic prophylaxis for women whose babies are at higher risk of developing GBS infection is currently the most effective method of preventing early onset GBS infection in the neonate.

    Risk factors for GBS infection in newborn babies are:

    • Mothers who have previously had a baby infected with GBS – risk is increased10 fold
    • Mothers who have been shown to carry GBS in this pregnancy or GBS has been found in the urine at any time during this pregnancy – risk is increased 4 fold
    • Each of the following clinical risk factors – risk of GBS infection is increased 3 fold
    • Labour starts or membranes rupture before 37 weeks of pregnancy is completed (i.e. preterm).
    • Where rupture of the membranes if prolonged: more than 18 hours before delivery.
    • Where the mother has a raised temperature* during labour of 37.8°C or higher.

    (Benitz et al Risk factors for early-onset group B streptococcal sepsis: estimation of odds ratios by critical literature review. Pediatrics. 2000 Aug;106(2 Pt 1):377-8)

    *If a woman has an epidural, a slightly raised temperature may be of less significance than in a woman with no epidural.

    NICE Antenatal Care Guideline CG62 states, “Pregnant women should not be offered routine antenatal screening for group B streptococcus because evidence of its clinical and cost effectiveness remains uncertain.”

    Routine testing of Mums for GBS carriage in pregnancy is not currently available on the NHS. The routine tests offered, say for an abnormal discharge, only pick GBS up about 50% of the time when Mum is carrying it. Although, if an NHS swab comes back as positive for GBS, you can be sure GBS as present when the swab was taken.

    There is a reliable test specifically developed to detect GBS carriage, called the Enriched Culture Method (ECM) test. It’s available privately and from a small but growing number of NHS trusts. Recognised as the ‘gold standard’ for identifying GBS carriage, the ECM test involves taking swabs from the vagina and rectum, which are analysed in a laboratory. In 2006, the Health Protection Agency issued a protocol describing this method for testing for GBS carriage httpo_O/www.hpa-standardmethods.org.u...pdf/bsop58.pdf .

    Although GBS carriage can come and go, a woman’s GBS status, determined by an ECM test, is not likely to change for about 5 weeks: research showed a positive ECM result gave an 87% chance she’d still be carrying GBS and a negative ECM result gave a 96% chance she’d not be carrying it 5 weeks later. So testing at 35-37 weeks of pregnancy is very good at predicting the chance of carrying GBS at delivery - earlier testing means the GBS status is more likely to change; later testing increases the chance the baby arrives before the test result.

    For how to obtain the ECM test (around £32 privately for a UK-wide postal service), ask your health professional or visit www.gbss.org.uk/test

    Preventing GBS infection in babies

    Giving women who carry GBS during the current pregnancy plus Mums in other higher risk situations intravenous antibiotics from the start of labour and at intervals until the baby is born is very effective at preventing GBS infection in newborn babies.

    Intravenous antibiotics should be given to Mum immediately at start of labour and then at intervals until delivery to prevent GBS infection in the newborn baby. The Royal College of Obstetricians and Gynaecologists recommends the antibiotics should be given for a minimum of 2 hours before delivery, although others (including Group B Strep Support) consider this the absolute minimum, with a period in excess of 4 hours being ideal.

    Intravenous antibiotics recommended for Mums in labour until delivery are:

    o Penicillin G: 3g (or 5MU) at first and then 1.5g (or 2.5MU) at 4-hourly intervals.
    o Clindamycin 900 mg every 8 hours for Mums allergic to penicillin.

    Researchers around the world are looking at developing a vaccine which, one day, could prevent most cases of early and late onset GBS infection. In the meantime, testing pregnant women during pregnancy for GBS carriage, then giving intrapartum antimicrobial prophylaxis to those carrying GBS plus to those with other risk factors would prevent more GBS infections in newborn babies than relying on risk-factors alone. (The prevention of neonatal group B streptococcal disease: a report by a working group of the Medical Screening Society. Law MR, Palomaki G, Alfirevic Z, Gilbert R, Heath P, McCartney C, Reid T, Schrag S. Journal of Medical Screening, 2005.)

    In the meantime, the incidence of GBS infection in newborn babies continues to increase. The Health Protection Agency (and formerly the CDR) reported 470 GBS infections in babies aged 0-90 days in 2008, an increase of 51% since 2003 (when RCOG's guidelines were introduced). That’s 3 more babies a week ... and this at a time when national prevention guidelines were being implemented.

    GBS infection in babies


    GBS infection usually shows in a baby’s first 6 days (early onset). Signs are apparent within 12 hours of birth in most babies and in the first 6 days for up to 90% of these sick babies. Early onset GBS infection in babies usually shows as bloodstream infection (sepsis), lung infection (pneumonia) and, less frequently, infection of the fluid and lining surrounding the brain (meningitis).

    Typical signs of early-onset GBS infection include:

    • Grunting.
    • Poor feeding.
    • Being abnormally drowsy (lethargic).
    • Being irritable.
    • High/Low temperature.
    • High/Low heart rate.
    • High/Low breathing rate.
    • Low blood pressure.
    • Low blood sugar.

    Most early-onset GBS infection can be prevented by giving intravenous antibiotics in labour to Mums whose babies are at increased risk.

    Late-onset GBS infection occurs after a baby’s first 6 days, is uncommon after a baby is one month old and is very rare after age three months. Late-onset GBS infection in babies usually shows as meningitis with septicaemia.

    Typical signs of late-onset GBS infection – including meningitis - may include one or more of:

    • High temperature, fever, possibly with cold hands and feet
    • Vomiting, refusing feeds or poor feeding
    • High pitched moaning, whimpering cry
    • Blank, staring or trance-like expression
    • Pale, blotchy skin
    • Floppy, may dislike being handled, be fretful
    • Difficult to wake or lethargic
    • Tense of bulging fontanelle (soft spot on babies’ heads)
    • Turns away from bright light
    • Altered breathing pattern
    • Involuntary stiff body or jerking movements

    There are no known ways of preventing late-onset GBS infection in babies – awareness is essential as early treatment is vital.


    Sources:


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