Group B streptococcus in labour — structured SAQ (15 marks)

(a) Indication and IAP regimen (3 marks)

One mark for the indication, one for the agent, one for the dose and route. ^[1]

• Indication: positive GBS vaginal-rectal culture at 36 weeks in a woman in established labour. The penicillin allergy does not change the indication — it changes the agent.^[1]
• Agent: intravenous clindamycin 900 mg every 8 hours. This is the appropriate alternative for a high-risk penicillin allergy (anaphylaxis to amoxicillin) with a GBS isolate known to be susceptible to clindamycin.^[1]
• Dose and route: clindamycin 900 mg intravenously every 8 hours, started at the onset of established labour and continued until delivery. The first dose should be given as soon as possible to maximise the chance of meeting the 4-hour adequacy window.^[2][1]

(b) Labour management and timing (3 marks)

One mark each for labour management, the timing rule, and the communication with the neonatal team. ^[1]

• Labour management: manage labour along standard obstetric lines. There is no requirement to expedite delivery for GBS prophylaxis alone, provided the antibiotics are started early enough. Continuous fetal monitoring is not required for GBS alone, but is appropriate if other intrapartum risk factors are present.^[2][1]
• The 4-hour timing rule: intrapartum antibiotic prophylaxis is considered adequate only when the antibiotic has been given at least 4 hours before delivery. The clindamycin should be started as early as possible in active labour to allow this window. The 4-hour window applies to all IAP agents, including clindamycin and vancomycin.^[1][3]
• Communication with the neonatal team: inform the neonatal team at the time of admission that this woman is GBS-positive with a penicillin allergy, and confirm the antibiotic regimen and the timing of administration in the handover at birth. The neonatal observation pathway depends on the adequacy of IAP.^[4][1]

(c) Revised regimen when the clindamycin susceptibility changes (4 marks)

One mark each for the recognition, the new agent, the dose, and the rationale. ^[1]

• Recognition: the re-reported isolate is non-susceptible to clindamycin. Clindamycin is no longer an appropriate agent for this woman, and the regimen must be revised immediately.^[1]
• New agent: intravenous vancomycin. Vancomycin is the only pharmacokinetically and microbiologically validated option for the penicillin-allergic woman with a non-susceptible isolate.^[1]
• Dose: vancomycin 20 mg per kilogram intravenously every 8 hours, with a maximum of 2 g per single dose. The dose should be based on weight and baseline renal function, with monitoring of trough levels if multiple doses are given.^[1]
• Rationale: clindamycin non-susceptibility means the agent will not achieve adequate bacterial killing at the site of action. Continuing clindamycin would expose the neonate to the risk of inadequately treated GBS colonisation. Erythromycin is no longer recommended for GBS prophylaxis because of rising resistance. Cefazolin is not appropriate for the high-risk penicillin allergy group.^[1]

(d) Neonatal communication and management at birth (5 marks)

Two marks for the adequate-IAP pathway, two for the inadequate-IAP pathway, one for the communication principle. ^[1][4]

• Communication principle: inform the neonatal team at birth of the maternal GBS status, the antibiotic regimen used (clindamycin then vancomycin), the reason for the change (non-susceptibility), and the timing of the last dose relative to delivery. This is the information the neonatal team needs to plan the observation and investigation pathway.^[4][1]
• If the revised regimen (vancomycin) was given more than 4 hours before delivery — adequate IAP. The neonate is observed on the postnatal ward with routine vital signs and feeding assessment, with no routine investigation and no empiric antibiotics, provided the neonate is clinically well at birth.^[4][1]
• If the revised regimen (vancomycin) was given less than 4 hours before delivery — inadequate IAP. The neonatal observation pathway differs by local guideline, but typically involves a longer period of observation (often 24 hours), limited investigation (blood culture, full blood count, CRP), and empiric antibiotics in selected cases (for example, if other risk factors are present or the neonate is symptomatic). The neonatal team makes the final decision on the observation and investigation pathway.^[1][4]
• A mark is available for stating that the maternal and neonatal teams should communicate directly at birth, with a written record of the GBS status, the regimen, and the timing of administration.^[4][1]