Amended Description of Haemophilus segnis Kilian 1977

A detailed amended description of Haemophilus segnis Kilian 1977 based on an examination of 22 strains, including the type strain, is presented. Included is information on ultrastructural characteristics, biochemical activities, fermentation end products, and deoxyribonucleic acid base composition. In a recent taxonomic study of 426 Haemophilus strains from human and animal origin, 17 strains isolated primarily from human saliva and dental plaque formed a separate group on the basis of their biochemical and other characteristics. The cell morphology, Gram reaction, requirement for the V-factor (nicotinamide adenine dinucleotide), and the ability to reduce nitrate confinned its inclusion in the genus Haemophilus. The distinguishing characteristics of this taxon, i.e., its feeble biochemical activity and the relatively high guanine-plus-cytosine (G+C) content of its deoxyribonucleic acid (DNA) (43.5 & 0.54 mol%) seemed to justify its recognition as a separate species within that genus. The name Haemophilus segnis (L. adj. segnis sluggish) was proposed (5). The name was validly published in the International Journal of Systematic Bacteriology (3). The present report provides an extended description of the biochemical and ultrastructural characteristics of H. segnis.