-also called Streptococcus agalactiae
-The most common cause of perinatal bacterial infection in the United States. E.coli is the second most common.
-Mechanism of transmission: The organism colonizes the birth canal and passes to the infant during labor and delivery. Also, hematogenous spread from mother to fetus.
-Mothers with GBS may have endometritis, chorioamnionitis, and UTIs.
-Screening: Vaginal and rectal cultures are done between 35 and 37 weeks of gestation. Women with positive cultures or a GBS UTI or bacteriuria will get intrapartum antibiotics with IV ampicillin.
Intrapartum Antibiotics for GBS
“Penicillin or ampicillin should be administered intravenously for intrapartum chemoprophylaxis against neonatal group B streptococcal infection. Cefazolin is an alternative in women with penicillin allergy who do not have a high risk of anaphylaxis.” AAFP
- Penicillin or Ampicillin
- Cefazolin (in women with PCN allergy without anaphylaxis).
- Vancomycin or Clindamycin is recommended for patients with PCN allergy at higher risk for anaphylaxis.
Dosages
Penicillin G 5 million units x 1 (initial dose), then 2.5 to 3 million units IV every four hours until delivery.
Ampicillin 2g IV x 1 (initial dose), then by 1 g every four hours until delivery.
Cefazolin 2g IV (initial dose), then 1g every four hours until delivery.
Clindamycin 900 mg IV every eight hours until delivery.
Vancomycin 1g every 12 hours until delivery.
NB: Clinda and Vanc should only be used in patients at high risk of anaphylaxis. Ie.e they had anaphylaxis, angioedema, respiratory distress, or urticaria after getting a PCN or cephalosporin in the past. For those people, don’t give them a PCN or cephalosporin. Use Clinda or Vanc.
Only use clindamycin if susceptibility testing results are back and show susceptibility to clindamycin. If not, use vancomycin instead.
Algorithm for Intrapartum antibiotics for GBS Prophylaxis from AAFP.
Reference
http://www.aafp.org/afp/2012/0701/p59.html#afp20120701p59-f5
CDC