Serum bactericidal effect on capsulated and non-capsulated Haemophilus influenzae in chronic sinusitis

Study on the incidence of bactericidal (BC) antibodies to a Haemophilus influenzae type b and a non-capsulated H. influenzae was carried out on sera from 50 healthy subjects, and from 30 patients with chronic sinusitis. Of the 50 sera from normal subjects, only one (2.0%) lacked BC antibodies to the H. influenzae type b, whereas 13 (26.0%) lacked BC antibodies to the non-capsulated H. influenzae. All of the 30 sera from patients with chronic sinusitis were bactericidal for the H. influenzae type b, whereas only three (10.0%) lacked BC antibodies to the non-capsulated H. influenzae. Specific IgG, IgM and IgA antibodies to the non-capsulated H. influenzae in serum were determined by the indirect fluorescent antibody assay. Of the 22 sera tested in this study, 15 (68.0%) had antibodies of at least the IgG, IgM, or IgA classes; with IgG occurring most often. These data suggest that a lack of circulating BC antibodies to both H. influenzae isolates is not associated with the chronic carriage of these organisms by patients with chronic sinusitis.