Use of IsoVitaleX[superscript tm] enrichment for the growth of Haemophilus somnus



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Texas Tech University


The effect of IsoVitaleX on the growth of ten strains of Haemophilus somnus was studied. A six to ten-fold increase in growth was observed as measured turbidimetrically when IsoVitaleX was added to a basal medium of brain-heart infusion broth to a final concentration of 1% (volume/volume). Thiamine pyrophosphate, a constituent component of IsoVitaleX, was found to be the growth promoting factor and would completely substitute for IsoVitaleX. An equal concentration (2.2 yM) of thiamine monophosphate promoted growth equal to that of thiamine pyrophosphate. Thiamine was nonstimulatory for all ten strains tested. When alkaline, thermal treated, brain-heart infusion broth was used as the basal medium, seven of the ten strains had an absolute requirement for thiamine monophosphate or thiamine pyrophosphate. The three remaining strains showed minimal growth when thiamine was added to this basal medium. However excellent growth was observed when thiamine monophosphate or thiamine pyrophosphate was utilized. Factor X (hemin) was found to further enhance the growth when concentrations of 5-10 yg/ml were coupled with thiamine pyrophosphate. No increase in growth was observed when factor V (nicotinamide adenine dinucleotide) was coupled with thiamine pyrophosphate. This is the first report of a growth factor requirement for Haemophilus somnus.