Heterogeneity among Dermatophilus congolensis isolates demonstrated by restriction fragment length polymorphisms.

There is evidence of antigenic diversity and of differences in virulence in Dermatophilus congolensis. For the understanding of the epidemiology of dermatophilosis it is important to distinguish between strains of the organism. Twenty field isolates from cattle in Chad and Cameroon, and an American reference strain, have been examined on restriction fragment length polymorphisms. After restriction enzyme digestion of DNA by BamHI and Southern blotting, a rDNA probe consisting of plasmid pMC5 carrying a 4.8 kb insert of Mycoplasma capricolum DNA coding for the 5S, 23S and part of 16S rRNA allowed to distinguish 6 ribotypes of D. congolensis, based on their hybridized rDNA patterns. Particular ribotypes may be distributed over a wide geographical area. On the other hand, strains belonging to at least 5 different ribotypes may be found in one herd; this may partly explain the lack of success in immunization against dermatophilosis in the field.