Abstract
Löwenstein-Jensen medium with mycobactin, cyclo-heximide, penicillin, and chloramphenicol, and enriched with sodium pyruvate, was compared with an ordinary L.-J. medium with mycobactin. Faeces samples from cattle experimentally infected with M. paratuberculosis were cultured on both media. The improved medium gave 11 % more positive cultures and 90 % more colonies. Of the positive cultures 97 % showed detectable growth after 8 weeks of incubation, and the contamination rate was reduced to 0.4 %. By culture of faeces samples from naturally infected cattle the improved medium identified 23.2 % more infected animals than the basic medium, mostly due to a reduction of the contamination rate to about 3 %.