Lack of pathogenicity of haemophili of the 'minor group' taxon for the gnotobiotic piglet.

After intranasal instillation two freshly isolated English strains of Haemophilus taxon 'minor group' produced persistent infection in the tonsil but failed to elicit macroscopic or histological changes in the lower respiratory tract of two pairs of 14-day-old gnotobiotic piglets whereas a freshly isolated English strain of Haemophilus pleuropneumoniae caused a lethal pleuropneumonia in a third pair.