Tryptone-yeast extract broth as a culture medium for Haemophilus pleuropneumoniae and Haemophilus parasuis to be used as challenge inocula.

Haemophilus pleuropneumoniae and Haemophilus parasuis were grown in a liquid medium containing tryptone and yeast extract. Whereas culture turbidity during exponential growth of either organism was proportional to the number of viable cells, continued incubation of stationary phase cultures was accompanied by a dramatic decrease in viability with no corresponding decrease in culture turbidity. It is concluded that the medium described should prove useful for the growth of porcine haemophili for use in experimental infections provided the stage of growth is given due consideration.