Correlations between leukocidin production and virulence of two isolates of Fusobacterium necrophorum.

Leukocidin production by Fusobacterium necrophorum was suggested to be an important element in the development of intraabdominal and liver abscesses in mice. Leukocidin production by cultures of F necrophorum was demonstrated by an in vitro assay. One of two isolates of F necrophorum was demonstrated to produce leukocidin. The leukocidin-producing strain was observed to be more infective than the nonleukocidin-producing strain (as demonstrated by abscess formation following intraperitoneal injection of immune-suppressed and normal mice). The infectivity of the leukocidin-producing strain was increased by successive passage in immune-suppressed mice. A simultaneous increase in leukocidin production was also demonstrated. The nonleukocidin-producing strain could not be passed effectively and was relatively noninfective for mice.