Mechanism of respiratory infection due to H.influenae and protection gainst this infection

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Haemophilus influenzae can cause a variety of both respiratory and systemic infections depending on the bacterial phenotype (encapsulated or unencapsulated). There is a possibility that oropharyngeal epithelial cells carrying cell-bound H.influenzae may exfoliate and enter the trachea, and produce infection in thelower respiratory tract. Accordingly, we have developed murine bronchopneumonia model with nontypable H.influenzae and sepsis/meningitis model with encapsulated (mainly type b) H.influenzae, using cell-bound organisms.In murine bronchopneumonia with -lactamase nonproducing and producing nontypable H.influenzae the efficacy of amoxicillin was obtained in the former model and that was not obtained in the latter model. This result indicates that we may be able to evaluate the in vivo activity of a drug in a new developed model.Furthermore, we studied the role of fimbriae on the pathogenesis of type bH.influenzae, using murine sepsis/meningitis. The mortality rate in fimbriated H.influenzae was higher than that in nonfimbriated H.influenzae. To the phagocytosis-killing activity of human sera, fimbriated H.influenzae organisms were more susceptible than nonfimbriated H.influenzae organisms. Moreover, the content of C3 bound to fimbriated organisms was more than to nonfimbriated organisms.