ANTIMICROBIAL SUSCEPTIBILITY OF RUMINAL STRAINS OF BUTYRIVIBRIO-FIBRISOLVENS

The susceptibility of five ruminal strains of Butyrivibrio fibrisolven s to 23 antimicrobial compounds was examined to evaluate effects of an timicrobials on this bacterium. All strains were very sensitive to ion ophores and inhibitors of protein synthesis, except for aureomycin. On the contrary, butyrivibrios were relatively insensitive to inhibitors of carbohydrate metabolism and uncouplers. The strains studied displa yed considerable variation in sensitivity to salinomycin, aureomycin a nd bacitracin. The substrate used to support the bacterial growth (glu cose or xylose) influenced the susceptibility of isolates to antimicro bial agents. In one third of the measurements inhibitory concentration s of antimicrobial compounds were lower with xylose-grown than with gl ucose-grown cells. Different response of xylose-grown cultures to anti microbials may reflect lower energy supply from fermentation of xylose which was metabolized more slowly and with lower biosynthetic efficie ncy.