Molecular genotyping of multinational ovine and caprine Corynebacterium pseudotuberculosis isolates using pulsed-field gel electrophoresis.

Caseous lymphadenitis (CLA) is a chronic, suppurative disease, with a worldwide distribution, caused by Corynebacterium pseudotuberculosis. The clinical manifestation of CLA is known to vary between different countries, and has been postulated to be due to differences in the strains present in these countries. Forty-two sheep and goat isolates of C. pseudotuberculosis from Australia, Canada, Eire, The Netherlands and Northern Ireland were characterized by pulsed-field gel electrophoresis (PFGE), biotyping, antimicrobial susceptibility, and production of phospholipase D. The PFGE-determined genotypes of this multicentric collection were then compared with representative ovine and caprine isolates from a previously published panel of PFGE profiles of United Kingdom isolates. Digestion with SfiI generated 16-18 bands in the 48.5 and 290 kb range, and differentiated four distinct pulsotypes amongst the 36 ovine and 6 caprine strains which displayed remarkable homogeneity. Based on these results, it would appear that the genome of C. pseudotuberculosis is highly conserved, irrespective of the country of strain origin.