5. Strep B in pregnancy

Question 1

what is Streptococcus Agalactiae

Answer 1

• Group B Streptococcus (GBS)
• Gram positive bacteria
• Commensal in gastrointestinal/genitourinary tract
• Opportunistic pathogen (elderly, immunocompromised and infants) not bad all the time but if has the oppourtunity will be come oppourtunistic
• Is beta hemolytic: breaks down red blood cells

Question 2

what are the implications of strep b

Answer 2

• Infection in neonates causes sepsis leading to pneumonia, meningitis, shock or even death
• Estimated pooled global incidence is 0.49 per 1000 births, including GBS-associated preterm birth, stillbirth, and neonatal infection
• GBS disease classified based on the time of onset:
• Early onset occur at less then 7 days of life (vertical transmission), happens in utero and from a colonised mother during delivery. 115 per year (2015)
• Late onset occurs later than 7 days of life (horizontal transmission - non hereditary transmission) so nosocomial or community transmission. 57 per year (2015)

Question 3

transmission (early onset)

Answer 3

• Approx. 50% of newborns with GBS +ve mothers will be colonised during birth in the absence of preventive measures, with 1 - 2% of these resulting in invasive disease
• Two route of infection
  ○ Infection can be from ascending placental and uterine infection. more rare
  ○ Most common route is gong through birth canal and becoming infected
• This can lead to a penetration of the blood brain barrier and cause meningitis
• Can cause bacteraemia and sepsis
• Can cause pneumonia and lung injury

Question 4

Antenatal screening
risk based

Answer 4

• Risk based:
  ○ fever of 38* of more, preterm birth, ruptured membrane more than 18h,
  ○ GBS bacteriuria eg urinary tract infection
  ○ Previous GBS disease in other births

Question 5

Antenatal screening
risk based

Answer 5

• Risk based:
  ○ fever of 38* of more, preterm birth, ruptured membrane more than 18h,
  ○ GBS bacteriuria eg urinary tract infection
  ○ Previous GBS disease in other births
• Any positive result will result in a intrapartum antibiotic prophylaxis (IAP) a minimum of 4 hours before delivery

Question 6

antenatal screening universal

Answer 6

• Universal screening (more prevalent in WA and AUS)
  ○ Vaginal and rectal swab at around 36 weeks gestation
  ○ Culture or molecular screening for BGS colonisation
  ○ It is either present or absent
  ○ Found to reduce the risk of GBS more than risk-based screening

Question 7

preventative measures for strep b

Answer 7

• Any positive result will result in a intrapartum antibiotic prophylaxis (IAP) a minimum of 4 hours before delivery
• Want screening as close to birth as possible
• Screening is viable for about 5 weeks
• therefore administration is different for term vs pretem babies

Question 8

antibiotic selection for strep B

Answer 8

• Treatment is usually penicillin
  ○ Only few cases have built penicillin resistance
• If you have low, high or unknown risk of penicillin allergy different routes are considered
• High risk treatment (clindamycin antibiotic) GBS is becoming resistant to the drug

Question 9

Antibiotic implications

Answer 9

Selectivity
- Antibiotics have off-target impacts which can impact the microbiome

Resistance
- Always a potential issue
- WHO listed clindamycin-resistant GBS as a pathogen of concern

Safety/Unknown effects
- Antibiotics are poorly tested for use in pregnancy
- Antibiotics are our current prophylaxis, but targeted alternative therapies should be explored
- Seeing issues with supply and demands with antibiotic shortages
Dysbiosis

Question 10

Vaccination

Answer 10

• Maternal vaccination to transfer maternal antibodies to the fetus before delivery
• If present at appropriate levels, antibodies could protect against GBS
• Vaccination window between 2nd and 3rd trimester as that’s when antibodies are strongest for birth
• The vaccination target is he capsule of polysaccharides which sit around the GBS molecule. There are ranges 1-9 of these serotypes and they all vary geographically (around the world)

Question 11

GBS vaccine development

Answer 11

• Is a preventative strategy
• Cost effective reduces screening costs and for developing countries
• Can potentially positively effects late onset GBS
• Requires epidemiology
  Safety during pregnancy and long term impacts require testing

Question 12

probiotics for GBS

Answer 12

• Need clinical to with robust power to discover the effects of probiotics
• Using beneficial bacteria as competition for BGS
• Administration of probiotics during pregnancy, namely in the third trimester, was associated with a reduced GBS recto-vaginal colonization at 35–37 weeks and a safe perinatal profile
• Organism used, visibility, administration and dose all need to be considered
• Is eradication the goal?
• Current proposed use: during to prevent GBS and after GBS treatment to restore beneficial bacteria

Question 13

Bacteriophage therepy for GBS

Answer 13

• Bacteriophages or phages are viruses and the natural predators of bacteria
• Phages are ubiquitous with an estimated 1 trillion per grain of sand on Earth
• They kill a specific host range of bacteria, but are unable to infect human cells
• An ideal treatment option would target GBS and no other organisms which are helpful
• Provides answer to antibiotic resistance
  Highly specific
• found in sewer

Question 14

GBS summary

Answer 14

• Group B Streptococcus is the leading cause of neonatal sepsis
• Transmission can occur during pregnancy, therefore mothers are screened and treated prophylactically – highly effective for Early Onset Disease
• Up to 30% of pregnant women will receive antibiotic prophylaxis for GBS
• Implications of antibiotic use to consider include resistance and dysbiosis (impact on the microbiome)
• Future prevention and treatment strategies need to be targeted, such as vaccination or bacteriophage therapy