Production of cytolethal distending toxin (CLDT) by Campylobacter fetus subsp. fetus isolated from calves.

Cytolethal distending toxin (CLDT) production by Campylobacter fetus subsp. fetus isolated from calves was examined using CHO cells. Twenty-five of the 26 strains tested were positive for CLDT with titer of ranging 1:8 to 1:2,048. CLDT positive strains were divided into low and high cytotoxin titer groups. Isolates from diarrhea cases tended to produce a significant amount of CLDT compared with isolates from liver. CLDT produced by C. fetus showed no effect on Y-1 cells and was heat-labile and trypsin-sensitive.