Efficacy of human immunoglobulin and penicillin G in treatment of experimental group B streptococcal infection

In an effort to develop more effective therapy for neonatal group B streptococcal infections, penicillin G and human immune serum globulin (ISG), alone and in combination, were evaluated for their therapeutic efficacy against experimental group B streptococcal bacteremia and meningitis in newborn rats. Infected rats received either penicillin G (200 mg/kg/day), ISG (2 g/kg) or penicillin G (200 mg/kg/day) + varying doses of ISG (0.25 to 2 g/kg). All animals receiving ISG alone died; otherwise, mortality rates did not differ significantly (17-30%). Therapy with penicillin G alone and in combination with ISG was equally effective in completely eradicating group B streptococcal from blood and cerebrospinal fluid. However, combinations of penicillin G and ISG were significantly more beneficial than penicillin G alone, as shown by a significantly lower incidence of bacteremia at the end of 1 day of therapy and by greater opsonophagocytic activity in sera of animals receiving penicillin G + ISG. These findings indicate that administration of ISG in conjunction with penicillin G rapidly clears bacteria from blood, suggesting that ISG may be a useful adjunct to antimicrobial therapy of neonatal group B streptococcal disease.