[Differentiation of Haemophilus strains isolated from chickens. IV. Studies on the dissociation of Haemophilus paragallinarum].

Bacteria of 2 phenotypic forms of one strain of Haemophilus paragallinarum were morphologically, culturally, biochemically and serologically investigated. On transparent solid media bacteria of the M variant (mucoid) were capsulated and showed iridescence in oblique transmitted light throughout the first 8-14 hours of incubation. Iridescence disappeared completely after 36 hours incubation. Bacteria of this variant formed stable homogeneous suspensions in 0.15 M NaCl and an homogeneous cloudiness after growth in liquid media. A type specific soluble substance was found in fluid culture filtrates and in bacterial washings using the indirect haemagglutination test. Bacteria of the R variant (rough) derived by dissociation of iridescent colonies were not capsulated and showed no iridescence throughout 8-14 hours incubation (minus variant). This bacteria showed spontaneous agglutination in 0.15 M NaCl and a granular growth in liquid media. There were no biochemical differences between M and R variant. A type specific substance was not found in the R bacteria using the indirect haemagglutination test. In the plate agglutination test no serological reaction between anti-K-sera and M antigen were observed. R to M variation occurred in SPF chickens following intranasal inoculation of organisms of R cultures grown for 6 or 20 passages on solid medium.