Haemophilus influenzae type b colonization in household contacts of infected and colonized children enrolled in day care.

Strategies for management of children attending day-care facilities after a case of Haemophilus influenzae type b disease are controversial. The success of chemoprophylaxis in preventing subsequent cases has been variable. Failure of rifampin prophylaxis as currently recommended may result from usage limited to direct contacts of the index patient. This prospective study was designed to ascertain the extent of colonization in household contacts of colonized children attending day-care facilities with an index case of H influenzae disease. Outer membrane protein analysis was used to determine similarity between strains isolated from contacts and index patients. Of children attending six day-care facilities, 15% were colonized with subtypes of H influenzae identical with those of their respective index patients, and 7% of children were colonized with different subtypes. Colonization with identical outer membrane protein subtypes in children from day-care homes was more frequent than in the larger day-care centers (91% v 8%, P less than .00001). Within families of children with identical outer membrane protein subtypes, 25% of household members (17% of parents and 44% of siblings) were colonized despite lack of direct contact with the index patients. This colonization rate was comparable to that of household contacts of index patients (26%). Among household contacts of index patients, especially siblings, colonization with H influenzae tended to be lower if the patient attended day care than if the patient did not attend day care (17% v 73%; P = .05 for siblings). We have found that household contacts of colonized day-care children are a reservoir of H influenzae.(ABSTRACT TRUNCATED AT 250 WORDS)