Haemophilus influenzae type B disease in a day care center: Eradication of carrier state by rifampin

Two cases of invasive Haemophilus influenzae type B disease (meningitis and cellulitis) occurred during a 60-day period among 69 children (median age 18 months) attending a day care center in Fresno, Calif. Nasopharyngeal colonization rates for H influenzae type B were 49% in the children, 8% in family contacts of culture-positive children, and 0% in staff. Colonization by H influenzae type B was infrequent in two control populations of children: those attending day care centers in Fresno without known H influenzae type B disease, and healthy children not enrolled in day care centers. The isolates from the children in the index day care center were inhibited in vitro by low concentrations of trimethoprim-sulfamethoxazole, but therapy with this combination for seven to ten days was ineffective in eliminating H influenzae type B carriage in 73% of 26 treated children. In a second clinical trial, treatment for four days with rifampin eradicated H influenzae type B carriage in 14 of 16 culture-positive individuals, whereas carriage persisted in 6 of 7 children whose families initially declined rifampin therapy (χc² = 8.5, P < .004). When systemic H influenzae type B infection occurs in a closed population of young children, the risk of serious illness among contacts may be appreciably higher than in similar age children in the general population. Our data indicate that rifampin is effective in this clinical setting, and support the need for a larger, controlled clinical trial.