Further characterization of Haemophilus paragallinarum and Haemophilus avium

A total of 60 isolates of Haemophilus spp. from chickens, including four reference strains of H. paragallinarum and one of H. avium, were examined for their physiological and biochemical properties. The isolates could be placed into two groups. One group was identified as H. paragallinarum and consisted of 43 isolates including the four reference strains of H. paragallinarum. The other group was identified as H. avium and consisted of 17 isolates including the reference strain of H. avium. H. avium can be differentiated from H. paragallinarum by its possession of the enzymes catalase and alpha-glucosidase, capacity to grow in air, production of acid from galactose, and by the fact that its growth is not improved by the addition of chicken serum. In addition, the majority of H. avium isolates, unlike H. paragallinarum, possess a yellow pigment and produce acid from trehalose.