The role of elastase in the differentiation of Bacteroides nodosus infections in sheep and cattle.

Eighty-seven Bacteroides nodosus isolates were examined for elastase production by clearing of elastin particles in TAS agar medium. These included 54 ovine virulent isolates, 28 ovine benign isolates and five bovine isolates. In addition 22 ovine virulent, 16 ovine benign and two bovine isolates were examined for decline in proteolytic activity over a 13-day period in the degrading proteinase test using hide power-azure as substrate. There was a remarkable correlation between elastase production, relative stability of proteolytic activity in the hide powder-azure test and virulence of B nodosus. Ovine virulent isolates invariably produced elastase whereas ovine benign isolates and bovine isolates were elastase negative. Bovine isolates produced only mild lesions in the feet of challenged sheep.