Characterization of ruminal bacteria producing a toxin associated with a bovine paraplegic syndrome

We studied the ruminal population densities of bacteria in animals with and without bovine paraplegic syndrome (BPS). All bacterial counts were performed under strict anaerobiosis. Although the rumen bacterial density was around 10(9) bacteria/ml in animals, both apparently healthy or suffering from BPS, a shift towards Gram-negative strains occurred in animals with BPS. The toxin added to the cultures stimulated bacterial growth. Bacterial strains from the rumen could produce the toxin in vitro. Gram-positive bacteria differed in their ability to produce the toxin; Streptomyces bovis did not produce the toxin, while Lactobacillus vitulinum was an efficient producer. All Gram-negative bacteria tested could produce the compound.