[Biologic characteristics of mycobacterium strains isolated from cattle from herds with clinical paratuberculosis]

In the period from 1983 to 1986, bacteriological examination for paratuberculosis was performed in 263 samples of lymph nodes, intestinal mucous membrane and excrements of cattle, kept on a farm where clinical paratuberculosis occurred. Seventy-nine strains of mycobacteria were isolated during the culturing. On selective agar medium with mycobactin as the growth stimulator, 71 strains were isolated which had failed to grow on the conventional mycobacterium-culturing media. In the subculture, the dependence of mycobacteria on the mycobactin declined and the number of mycobacterium strains growing in the subculture on conventional mycobacting-free media doubled. Two thirds of the mycobacteria which did not depend on mycobactin during growth exhibited the same antigenic properties as Mycobacterium avium 1, 2, 3, 8 during serotypification. Ability to induce sensibility to PPD avian tuberculin or paratuberculin was demonstrated during the bioassays of mycobactin. Almost a half of the strains inducing animals' sensitivity to the above-mentioned allergens were found to be virulent to pullets that had tuberculosis in their parenchymatous organs. Of the laboratory animals, the highest virulence of the mycobactin-dependent mycobacterium strains was demonstrated in mice subjected to intravenous infection, accompanied by hyperplasia of the spleen, with reisolation of the mycobacterium culture within six eight weeks after infection.