Pharyngeal carriage rates of Haemophilus influenzae, type b and non-b, and prevalence of ampicillin-resistant Haemophilus influenzae among healthy day-care children in central Massachusetts.

Pharyngeal swabs were obtained from 832 children less than 14 years of age attending day-care centers and family day-care homes in central Massachusetts during a seven-week period beginning March 1, 1982. Colonization rates for Haemophilus influenzae and for H. influenzae type b were 60.7% and 15.1%, respectively. Nonwhite children were more likely to be carriers of non-b H. influenzae than white children (62.9% vs. 47.8%, p less than 0.025). Children in day care for more than six months were more likely to be carriers of non-b H. influenzae than children in day care for six months or less (52.9% vs. 45.5%, p less than 0.05). There was no association between colonization rates and age, sex, type of day-care setting, number of siblings, number sharing a bedroom, history of otitis media, or history of antibiotic use. The prevalence of ampicillin-resistant H. influenzae was 6.3% among all children and 10.3% among carriers of H. influenzae. The prevalence of ampicillin resistance was significantly higher among type b carriers than among carriers of other types (15.1% vs. 8.3%, p less than 0.05). Children who had taken ampicillin or amoxicillin within the past three months were much more likely to be colonized with ampicillin-resistant H. influenzae than were children who had not taken these antibiotics (13.5% vs. 4.8%, p less than 0.0005). These observations have important clinical implications for the management of children with H. influenzae disease.