Virulence and morphology of Pasteurella multocida of avian origin.

The virulence of 100, 54 and nine avian isolates of Pasteurella multocida for mice, chickens and turkey poults respectively was assessed and rated on a scale from 0 to 5. Cellular and colonial morphology of the bacteria was examined after mouse passage. There was evidence of a considerable range in the virulence of the isolates for the test species, but no correlation between cellular or colonial morphology and virulence was detected. The results obtained are discussed in relation to general epidemiological considerations.