Group B streptococcus (GBS) – screening and management

Group B streptococcus (GBS)

Practice points

• GBS is a transient bacterium that is commonly found in the gastrointestinal tract, vagina and urethra in 15-25% of pregnant women (asymptomatic carriers of GBS).
• GBS is transmitted to the baby during birth in approximately 1–2 per 1000 live births and can lead to serious infection in the baby.
• EOS may result in neonatal morbidity, including respiratory symptoms, pneumonia and sepsis. It can result in death of the baby if not detected and treated early.
• IAP can prevent EOS in up to 89 per cent of babies of colonised women (Lin et al. 2001; Schrag et al. 2002).
• A pregnant woman who tests positive for GBS and gets IAP has a one in 4000 chance of delivering a baby who will develop EOS, compared to a one in 200 chance if she does not have IAP (Centers for Disease Control and Prevention 2018).
• IAP does not prevent late onset sepsis (LOS).
• The decision to give antibiotic treatment in labour can be determined through:
  • consistent identification of clinical risk factors during pregnancy and labour
    or
  • taking a combined vaginal-rectal swab at 35-37 weeks gestation.
• Preterm babies are four times more likely to develop EOS than term babies (Kurz and Davis 2015).

Risk factors

Table 1. Obstetric risk factors for EOGBS infection

Practice points

• If any of the above risk factors are identified, IAP is recommended once active labour is identified.
• Aim for ≥4 hours of IAP coverage prior to birth.
• Antibiotic prophylaxis is not recommended prior to the onset of labour.

Antenatal screening

Practice points

• Maternity services across Australia use either a clinical risk-based or universal culture-based screening approach to reduce EOS in the baby.
• There is a lack of consensus and limited high quality evidence regarding a preferred approach.
• All maternity services should have an established plan for prevention of EOS. Follow organisational protocols and local guidelines.
• GBS, EOS and IAP should be discussed with the woman during the antenatal period in a manner that supports informed decision making.
• Clinicians must remain vigilant for signs of EOS as this can occur in a baby of culture-screened GBS negative women.

Risk-based management

• Discuss and document risk factors at booking.
• If the woman had a previous baby with invasive EOS, discuss and document the recommendation for IAP.
• If tests at any point in pregnancy show GBS colonisation or bacteriuria:
  • discuss results with the woman and document her status as GBS positive
  • discuss and document the recommendation for IAP
  • if GBS colonisation or bacteriuria is found incidentally or by intentional testing earlier in pregnancy, do not repeat investigation in later pregnancy.
• If other risk factors arise (see Table 1), IAP is recommended once active labour is identified.

Universal screening

• Undertake GBS culture based-screening, using combined vaginal-rectal swab at 35–37 weeks gestation if no risk factors or colonisation has been identified prior to this.
• Inform all women of the testing procedure and implications of results.
• If testing is carried out, tell the woman her results and document in antenatal records. Ensure that a woman with a positive result understands the importance of relaying this information to the health professionals who care for her in labour.
• Where universal screening is used, risk factors are still relevant as EOS can occur in culture-screened GBS negative women, so:
  • discuss and document risk factors at booking and plan for care accordingly
  • continue to assess for risk factors, GBS colonisation or bacteriuria arising later in pregnancy.
• Inform all women that if their screening result is GBS negative, the presence of risk factors will lead to IAP being recommended.

Specimen collection

• Swabs may be collected by a clinician or collected by the woman.
• Use one single dry swab stick:
  • insert into the vaginal introitus
  • then insert into the anus.
• Place into standard bacterial transport medium.
• Label specimen clearly with ‘GBS screening in pregnancy’.
• Request sensitivity screening for women who are allergic to penicillin.

Intrapartum management

Identification of risk factors

Practice points

• If risk factors (Table 1) are identified on admission or at any point during labour:
  • discuss the recommendation for IAP with the woman
  • indicate the need for IAP on the partogram and in the progress notes/electronic medical record (EMR).
• Offer IAP to woman with risk factors irrespective of screening result.

Intrapartum antibiotic prophylaxis

See – Term PROM eHandbook page

See – PPROM eHandbook page

Practice points

• Recommend IAP to women with identified risk factors when active labour is identified: Intrapartum antibiotic prophylaxis flowchart.
• Antibiotic prophylaxis is not recommended prior to the onset of active labour.
• Adequate prophylaxis is considered to be commenced at least four hours prior to birth.
• Benzylpenicillin is the antibiotic of choice – IV penicillin and ampicillin are equally effective against GBS, but penicillin is preferable due to its narrower spectrum of activity.
• A GBS positive screening result is not a preclusion to labour in the bath or pool, or birth through water, as long as antibiotic prophylaxis occurs. 

Antibiotic regimen

• IV Benzylpenicillin 3 g loading dose

then

• IV Benzylpenicillin 1.8 g every four hours until birth.

If the woman has a penicillin hypersensitivity with no history of anaphylaxis

• IV Cephazolin 2 g loading dose
  then
• IV Cephazolin 1 g every eight hours until birth.

If the woman has a penicillin allergy with history of anaphylaxis

• IV Clindamycin 900 mg every eight hours until birth.
• If sensitivity is unknown or GBS isolate is resistant to Clindamycin, administer IV Vancomycin 1 g every 12 hours until birth.

Clinical circumstances where IAP is not required

• GBS carriage detected in a previous pregnancy (even if GBS status is unknown in the current pregnancy).
• Elective caesarean section (no labour, no rupture of membranes) irrespective of GBS carriage or gestational age.
• For women where routine surgical antibiotic prophylaxis for CS is indicated.
• Threatened preterm labour with intact membranes, where the risk of imminent birth is low.

Postnatal management

Neonatal care

Practice points

• GBS is the most frequent cause of early onset neonatal sepsis in developed countries.
• Signs of EOS are non-specific and can include respiratory distress, temperature instability, tachycardia, shock, or ‘unwell’  and most likely to arise within 24 hours of birth.
• Treat all unwell babies for suspected sepsis, irrespective of maternal GBS status or adequate IAP.

Observation and management

• Observations as per GBS: Neonatal management flowchart
• Record observations on a track and trigger chart
• Escalate care as per local guidelines.

Advice for future pregnancy

Advise the woman that:

• if she has GBS colonisation in this pregnancy but without infection in the baby, pregnancy and birth management is not affected in her next pregnancy
• if her baby has been diagnosed with EOS:
  • IAP is recommended during her  next labour
  • her next baby has an increased risk of EOGBS disease and will most likely be offered antibiotic prophylaxis
  • she is able to discuss the impact on future pregnancies with the paediatric/neonatal team
  • she should inform future care providers that she has had a baby with EOS.

Audit and performance improvement

All maternity services should have processes in place for:

• auditing clinical practice and outcomes
• providing feedback to clinicians on audit results
• addressing risks, if identified
• implementing change, if indicated.

Potential auditable standards include:

• adherence to standards of care
• GBS screening rates.

References

• Centers for Disease Control and Prevention (CDC) 2018, ‘Preventing early-onset group B strep disease’, [Internet : viewed May 2019], https://www.cdc.gov/groupbstrep/about/prevention.html
• Kurz, E and Davis, D 2015, ‘Routine culture based screening versus risk based management for the prevention of early onset group B streptococcus disease in the neonate : a systematic review’, Joanna Briggs Institute Database of Systematic Review & Implementation Reports, vol. 13, no. 3, pp. 206-46. DOI: 10.11124/jbisrir-2015-1876.
• Lin FY, Brenner RA, Johnson YR, Azimi PH, Philips JB 3rd, Regan JA, Clark P, Weisman LE, Rhoads GG, King F &Clemens JD 2001, ‘The effectiveness of risk-based intrapartum chemoprophylaxis for the prevention of early-onset neonatal group B streptococcal disease’. American Journal of Obstetrics and Gynaecology 1, vol. 184, no. 6, pp. 1204-10, DOI: 10.1067/mob.2001.113875.
• Schrag SJ, Zell ER, Lynfield R, Roome A, Arnold KE, Craig AS, Harrison LH, Reingold A, Stefonek K, Smith G, Gamble M, Schuchat A; for the Active Bacterial Core Surveillance Team 2002. ‘A population-based comparison of strategies to prevent early-onset group B streptococcal disease in neonates’, New England Journal of Medicine, vol. 347, no. 4, pp. 233–39, DOI: 10.1056/NEJMoa020205.

Bibliography

• American College of Obstetricians and Gynecologists 2011, ‘Prevention of early-onset group B streptococcal disease in newborns’, Obstetrics Gynecology, Committee Opinion No. 485. vol. 117, pp.1019-27.
• Australasian Society for Infectious Diseases 2014, ‘Management of perinatal infections’, [Internet: viewed May 2019]. available from: https://www.asid.net.au
• Berardi A, Rossi C, Guidotti I, Vellani G, Lugli L, Bacchi Reggiani ML, Ferrari F, Facchinetti F & Ferrari F 2014, ‘Factors associated with intrapartum transmission of group B Streptococcus’, Pediatric Infectious Disease Journal, vol. 33, no. 12, pp. 1211-5, DOI: 10.1097/INF.0000000000000439.
• Centers for Diseases Control and Prevention 2010, ‘Prevention of perinatal Group B streptococcal disease; revised guidelines’, Morbidity and Mortality Weekly Report, vol. 59, no. RR-10, [Internet: viewed May 2019], available from: https://www.cdc.gov/mmwr/pdf/rr/rr5910.pdf
• Darlow BA, Voss L, Lennon DR & Grimwood K 2016, ‘Early-onset neonatal group B streptococcus sepsis following national risk-based prevention guidelines’, Australian & New Zealand Journal of Obstetrics & Gynaecology, vol. 56, no.1, pp. 69-74. DOI: 10.1111/ajo.12378
• Department of Health 2018, Clinical Practice Guidelines: Pregnancy Care, Canberra, Australian Government Department of Health, [Internet: viewed May 2019], available from: https://beta.health.gov.au/resources/pregnancy-care-guidelines
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• Lin FY, Weisman LE, Troendle J & Adams K 2003, ‘Prematurity is the major risk factor for late-onset group B streptococcus disease’, Journal of Infectious Disease, vol. 188, no. 2, pp. 267-71.
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• Perinatal Clinical Practice Guidelines Working Party 2010, Clinical Practice Guideline - Prevention of neonatal early onset group B streptococcal disease. Brisbane: Queensland Health, [Internet: viewed May 2019], available from: https://www.health.qld.gov.au/qcg/publications
• Royal Women’s Hospital 2018, Clinical Guideline: GBS Colonisation: Management of Infant to Prevent Early Onset Group B Streptococcus (EOGBS) Disease, [Internet: viewed May 2019], from:  https://www.thewomens.org.au/health-professionals/clinical-resources/clinical-guidelines-gps#
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