Antigenic structures of Haemophilus aegyptius and Haemophilus influenzae demonstrated by the gel precipitation technique.

Until 1950 the differentiation of the KochWeeks bacillus and Haemophilus influenzae had not been well defined and their identity as separate species or single species has been controversial. However the results reported by Pittman and Davis (1950) showed that the Koch-Weeks bacillus, Haemophilus aegyptius, is a distinct species that can be separated from H. influenzae by serological means and, to a certain extent, by growth characteristics and biochemical reactions. Since all of the strains described by Pittman and Davis were isolated from the eyes of patients with conjunctivitis in the United States, it seemed to be worthwhile to examine further strains in the Near East, where Koch (1883) had first described the organisms found in the pus of an individual having a benign form of acute conjunctivitis. An investigation of Huet and Benslama (1956) in Tunis identified 3 of 120 Haemophilus strains isoated from cases of conjunctivitis as H. influenzae, 10 as H. parainfluenzae, whereas the other strains constituted a nonhomogenous group and did not show the characteristics of H. aegyptius as described by Pittman and Davis (1950). We, therefore, started examinations aimed at determining whether the strains which appear seasonally in summer epidemics in Israel are identical with those described by Pittman and Davis (1950) as H. aegyptius. The serological examinations reported below constitute a part of this work. In these experiments we followed, with slight modifications, the technique described by Ouchterlony (1948). This same technique was employed in studies on the antigenic structure of H. influenzae by Tunevall (1953).