Haemophilus Species

Authored by: Elisabeth Adderson

Practical Handbook of Microbiology

Print publication date:  June  2015
Online publication date:  June  2015

Print ISBN: 9781466587397
eBook ISBN: 9781466587403
Adobe ISBN:


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The genus Haemophilus currently includes 12 species: H. aegyptius, H. ducreyi, H. felis, H. haemoglobinophilus, H. haemolyticus, H. influenzae, H. paracuniculus, H. parahaemolyticus, H. parainfluenzae, H. paraphrohaemolyticus, H. parasuis, and H. pittmaniae (International Subcommittee on the Taxonomy of Pasteurellaceae 2012). Robert Pfeiffer first described the type species, H. influenzae, during the 1889–1892 influenza pandemic, and until 1918, it was assumed to be the etiologic agent of these infections. The taxonomy of the genus has evolved rapidly with the availability of sensitive genotyping methods. The most recent changes include the recognition that H. aphrophilus and H. paraphrophilus are synonymous and that these strains, along with H. segnis, are more appropriately classified within a distinct genus, Aggregatibacter gen. nov., as Aggregatibacter aphrophilus comb. nov. and Aggregatibacter segnis comb. nov. (Norskov-Lauritsen and Kilian 2006). Genotypic and phenotypic studies have also led to the reassignment of H. paragallinarum and H. (Pasteurella) avium to a novel genus, Avibacterium gen. nov., as A. paragallinarum comb. nov. and A. avium comb. nov. (Blackall et al. 2005). Significant phenotypic and genotypic differences suggest that while it currently remains a member of the genus, H. ducreyi would be more properly recognized as a distinct member of Pasteurellaceae (Sturm 1981). The inclusion of H. parainfluenzae, H. haemoglobinophilus, H. parahaemolyticus, H. parasuis, H. paraphrohaemolyticus, H. paracuniculus, and H. felis in the genus is also the focus of current consideration. H. aegyptius and nonencapsulated H. influenzae may be indistinguishable by standard differential tests, but are genetically distinct and continue to be regarded as separate species. Haemophilus species causing human disease include H. influenzae, H. aegyptius, H. ducreyi, H. haemolyticus, H. parahaemolyticus, H. parainfluenzae, H. paraphrohaemolyticus, and H. pittmaniae.

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