IV Treatment for Group B Streptococcus Infections

First-Line Treatment Options

The Centers for Disease Control and Prevention recommends penicillin G as the first-line IV treatment for GBS infections, with an initial dose of 5 million units IV followed by 2.5-3.0 million units every 4 hours, or alternatively ampicillin 2 g IV initial dose then 1 g every 4 hours 1
For patients without penicillin allergy, the American College of Obstetricians and Gynecologists suggests penicillin G: 5 million units IV loading dose, then 2.5-3.0 million units IV every 4 hours until delivery 1
The American College of Obstetricians and Gynecologists also recommends ampicillin: 2 g IV loading dose, then 1 g IV every 4 hours until delivery 1

For low-risk penicillin allergy patients, the Centers for Disease Control and Prevention recommends cefazolin: 2 g IV loading dose, then 1 g IV every 8 hours until delivery 1, 2
The Infectious Diseases Society of America notes that cefazolin is preferred because pharmacologic data demonstrate effective intraamniotic concentrations 2
The Centers for Disease Control and Prevention states that approximately 10% cross-reactivity risk exists between penicillin and cephalosporins 2

If GBS isolate is susceptible to both clindamycin AND erythromycin, the Centers for Disease Control and Prevention recommends clindamycin 900 mg IV every 8 hours until delivery 1, 2
If susceptibility unknown or isolate resistant, the American College of Obstetricians and Gynecologists suggests vancomycin 1 g IV every 12 hours until delivery 1, 2
The Centers for Disease Control and Prevention warns that resistance to erythromycin often indicates inducible clindamycin resistance, even if the isolate appears susceptible to clindamycin 1

The American College of Obstetricians and Gynecologists notes that standard GBS prophylaxis regimens may be insufficient for chorioamnionitis 1, 3
The Infectious Diseases Society of America recommends broader spectrum agents active against GBS and other organisms, including E. coli and gram-negative pathogens, for chorioamnionitis 1

The American Academy of Family Physicians states that intrapartum antibiotic prophylaxis is effective within 2-4 hours of administration 4
The Centers for Disease Control and Prevention recommends at least 4 hours of IV antibiotics before delivery for adequate neonatal protection 1
The Infectious Diseases Society of America warns that many reported penicillin allergies are not true IgE-mediated reactions, and detailed allergy history can identify patients who can safely receive penicillin rather than alternatives 2
The Centers for Disease Control and Prevention notes that when clindamycin is considered for high-risk allergy patients, both clindamycin AND erythromycin susceptibility must be confirmed 1, 2