DICHELOBACTER NODOSUS - DIFFERENTIATION OF VIRULENT AND BENIGN STRAINS BY GENE PROBE BASED DOT-BLOT HYBRIDIZATION

Gene probes specific for benign and virulent strains of Dichelobacter nodosus were used in a dot blot hybridisation procedure involving 96 s trains of D. nodosus isolated from cases of ovine footrot. The perform ance of the probes was compared with that of the elastase test. All 27 strains with elastase activity at 7 days and 12 of 25 strains with el astase activity at 14 days reacted with the virulent-specific probe. T wenty-four strains with elastase activity between 21-28 days, and 20 s trains with negative elastase activity up to 28 days did not bind with this probe. On the other hand, the benign-specific probe failed to bi nd with the 27 strains with elastase activity at 7 days, and 13 of the 25 strains with elastase activity at 14 days but reacted with 20 of t he 24 strains with elastase activity at 21-28 days, and 19 of the 20 s trains with negative elastase activity up to 28 days. The 12 strains w ith elastase activity at 14 days which were detected by the virulent-s pecific probe were not those recognised by the benign-specific probe. The use of virulent and benign specific gene probes in combination pro vides a rapid and precise screening system for differentiation of viru lent and higher intermediate footrot from benign and lower intermediat e footrot.