From the FDA Drug Label
Serious infections, such as pneumonia and endocarditis, due to susceptible strains of streptococci (including S pneumoniae) and meningococcus 150,000 - 300,000 units/kg/day divided in equal doses every 4 to 6 hours; duration depends on infecting organism and type of infection The recommended treatment for Strep agalactiae bacteremia is penicillin G (IV) with a dosage of 150,000 - 300,000 units/kg/day divided in equal doses every 4 to 6 hours. The duration of treatment depends on the infecting organism and type of infection 1.
From the Research
The recommended treatment for Streptococcus agalactiae (Group B Streptococcus) bacteremia is intravenous penicillin G at a dose of 4 million units every 4 hours for adults, or ampicillin 2 grams IV every 4-6 hours, typically for a duration of 10-14 days. For patients with penicillin allergy, vancomycin 15-20 mg/kg IV every 8-12 hours (not exceeding 2 grams per dose) is the preferred alternative, as supported by a study from 2 which found all GBS strains to be sensitive to Penicillin, Ampicilin, and Vancomycin. The treatment duration may be extended to 4-6 weeks if there are complications such as endocarditis or osteomyelitis. Source control is essential if there is an identifiable focus of infection, which may require drainage of abscesses or removal of infected devices. Blood cultures should be repeated to confirm clearance of bacteremia. Group B Streptococcus is generally susceptible to beta-lactam antibiotics, making penicillin the drug of choice due to its narrow spectrum and excellent activity against the organism, as noted in 3. The high doses are necessary to ensure adequate penetration into all tissues, particularly if there is concern for meningeal involvement or endocarditis. It's also important to consider the increasing resistance to non-beta-lactam antibiotics, including clindamycin and erythromycin, as observed in 4 and 5, which highlights the need for careful selection of alternative antibiotics in patients with penicillin allergy. Overall, the choice of antibiotic and duration of treatment should be guided by the severity of the infection, the presence of any complications, and the patient's individual risk factors, as well as susceptibility patterns, as discussed in 2, 4, 3.