Evaluation of serum bactericidal antibody assays for Haemophilus influenzae serotype a.

Haemophilus influenzae type a (Hia) is an important pathogen for some American Indian, Alaskan native, and Northern Canada aboriginal populations. Assays to measure serum bactericidal activity (SBA) to Hia have not been developed or validated. Here, we describe two methods for the measurement of SBA: SBA with a viability endpoint (CFU counts) and SBA with a fluorometric endpoint using alamarBlue as the metabolic indicator. Both SBA assays measure Hia-specific functional antibody and correlate with anti-Hia IgG enzyme-linked immunosorbent assay (ELISA) concentration of naturally acquired antibodies.