COMPARISON OF GENE PROBE AND CONVENTIONAL METHODS FOR THE DIFFERENTIATION OF OVINE FOOTROT ISOLATES OF DICHELOBACTER-NODOSUS

In a collaborative study that involved four Australian veterinary diag nostic laboratories a gene probe test based on the recombinant plasmid s pJIR318, pJIR314B, and pJIR313, which contain genomic vap or vrl reg ions, was compared with conventional tests used for the differential d iagnosis of ovine footrot. A total of 771 clinical Dichelobacter nodos us isolates were tested and designated as belonging to one of several gene probe categories. The results showed that 87% of the virulent iso lates belonged to gene probe category 1, compared to only 6% of the be nign isolates. It was concluded that there was good correlation betwee n the gene probe test and the virulence designation of these isolates as well as the results of elastase, gelatin-gel and protease isoenzyme tests. Furthermore, the gene probe test was converted to a polymerase chain reaction (PCR)-based test. It is suggested that diagnostic labo ratories consider carrying out both this PCR test and tests based on t he extracellular proteases of D. nodosus.