NASOPHARYNGEAL COLONIZATION WITH HAEMOPHILUS-INFLUENZAE TYPE-B AMONG INFANTS AND CHILDREN IN JAPAN

Healthy carriers of Haemophilus influenzae type b (Hib) play an import ant role in the spread of invasive Hib disease. The aim of the present study was to estimate Hib colonization among infants and children in Japan. Specimens from throat and nasopharyngeal cultures were obtained by thorough swabbing of both tonsils and the posterior pharynx. Speci mens were inoculated on Hib antiserum agar. This was prepared with Lev inthal base and Hib antiserum. Conventional methods were used concomit antly. Four of 474 infants from 1-48 months of age (0.84%) had Hib cul tured from their nasopharynx. The carriage rate in 1-12 month old infa nts was 0.62% (2/322 cases), and that in 13-48 month old children was 1.32% (2/152 cases). Five of 167 (3.0%) 13-year-old children, and five of 154 (3.2%) 9-year-old children were asymptomatic carriers. Thirty- five of 104 household contacts of a patient with invasive Hib disease (33.6%) had Hib colonization. The carriage rate in healthy Japanese ch ildren may not be different from that in the USA prior to the availabi lity of the conjugate Hib vaccine. The Hib carriage rate in household contacts of patients with invasive Hib disease was higher than in heal thy children (P < 0.005). Our results suggest the possibility of an ou tbreak of invasive Hib disease in Japan.