'Haemophilus gallinarum'--a re-examination.

Area of Science:

• Veterinary Microbiology
• Bacterial Pathogenesis

Background:

• Historical classification of avian haemophili strains, including 'Haemophilus gallinarum', has relied on growth factor dependencies.
• Previous studies from the 1930s suggested the existence of X- and V-factor-dependent avian haemophili, implicated as the cause of infectious coryza.

Purpose of the Study:

• To re-examine the growth factor requirements and characteristics of long-stored avian haemophili strains.
• To investigate the accuracy of historical findings regarding X- and V-factor dependency in avian haemophili.

Main Methods:

• Culturing and biochemical characterization of two historical avian haemophili strains.
• Replication of historical experimental methodologies used to determine growth factor dependency.
• Serological and pathological property analysis of the examined strains.

Main Results:

• Both historical strains were found to be X-factor independent and V-factor dependent.
• These strains exhibited biochemical, serological, and pathological properties consistent with *Haemophilus paragallinarum*.
• Replication of historical methods caused X-factor independent strains to appear X- and V-factor dependent, indicating a methodological artifact.

Conclusions:

• The classification of early avian haemophili as X- and V-factor dependent appears to be incorrect.
• Historical findings on the etiological agent of infectious coryza may have been based on flawed methodology.
• The studied strains are likely *Haemophilus paragallinarum*, not a distinct X- and V-factor dependent species.