LOW GENETIC DIVERSITY OF HAEMOPHILUS-INFLUENZAE TYPE-B COMPARED TO NONENCAPSULATED HAEMOPHILUS-INFLUENZAE IN A POPULATION IN WHICH HAEMOPHILUS-INFLUENZAE IS HIGHLY ENDEMIC

Immunization with Haemophilus influenzae type b (Hib) conjugate polysa ccharide vaccines has dramatically reduced Hib disease worldwide. As i n other populations, nasopharyngeal carriage of Hib declined markedly in Aboriginal infants following vaccination, although carriage has not been entirely eliminated. In this study, we describe the genetic char acteristics and the carriage dynamics of longitudinal isolates of Hib, characterized by using several typing methods. In addition, carriage rates of nonencapsulated H. influenzae (NCHi) are high, and concurrent colonization with Hib and NCHi is common; we also observed NCHi isola tes which were genetically similar to Hib. There is a continuing need to promote Hib immunization and monitor H. inflluenzae carriage in pop ulations in which the organism is highly endemic, not least because of the possibility of genetic exchange between Hib and NCHi strains in s uch populations.