Three variants of the leukotoxin gene in human isolates of Fusobacterium necrophorum subspecies funduliforme

•The leukotoxin gene was detected in 220 human isolates of F. necrophorum.•Three sequence variants were detected, two of which have not been previously described.•The novel sequence types were found in the majority of the isolates.•The sequence types correlated to the source of infection.

Leukotoxin is a well-known virulence factor of animal isolates of Fusobacterium necrophorum subspecies necrophorum, and is also expressed by animal isolates of subspecies funduliforme, whereas its presence in isolates from humans has not been fully established. In this study we found that the leukotoxin gene was present in all tested F. necrophorum isolates from humans. Three sequence variants were found, two of which have not been described previously. The sequence types correlated to source of infection. Further studies are needed to examine the role of the leukotoxin in human infections.