Failure of rifampin to eradicate group B streptococcal colonization in infants

BACKGROUND.Mucous membrane colonization with group B streptococci (GBS) frequently persists in infants after treatment of invasive infection and may be associated with recurrent disease. OBJECTIVE.To determine the frequency with which GBS colonization persists at mucous membrane sites after treatment of invasive early or late onset infection and to determine the efficacy of oral rifampin in eradicating colonization in these infants and their mothers. METHODS.Cultures for isolation of GBS were obtained from infants and their mothers after completion of the infant’s parenteral therapy, 1 week later when rifampin therapy was initiated and at ∼1 and 4 weeks after completion of rifampin therapy. Rifampin was administered (10-mg/kg dose; maximum, 600 mg) twice daily for 4 days. RESULTS.Ten of 21 infants (48%) and 13 (65%) of their 20 mothers were colonized with GBS at throat or rectal (infant) or vaginal, rectal or breast milk (mother) sites before rifampin was initiated. One week or less after rifampin treatment, 7 (70%) infants and 4 (31%) mothers remained colonized with GBS. At study completion 6 infants and 7 mothers had GBS colonization. Persistent colonization was not related to GBS serotype, to initial rifampin minimal inhibitory concentration or to the development of rifampin resistant strains. CONCLUSIONS.Rifampin treatment for four days utilized as a single agent after completion of parenteral therapy failed to reliably eradicate GBS colonization in infants.