Influence of Starch in Media Used for the Detection of Heated Bacterial Spores


DURING investigations of the heat resistance of the spores of several Australian strains of Clostridium botulinum, it was found that various agar media gave divergent estimates of spores surviving heat treatment, even though each medium indicated similar numbers of viable spores in the unheated suspension. An attempt was made, therefore, to prepare a medium which would be reliable for the detection or spores surviving heat treatment. It has now been shown that the addition of small amounts of starch to media increases the number of colonies which develop from an inoculum of heated spores. Several types of natural starches produce similar effects in different infusion media suitable for the growth of Cl. botulinum. The influence of different concentrations of soluble starch added to pork infusion thioglycollate agar1 is shown in the accompanying graph.


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OLSEN, A., SCOTT, W. Influence of Starch in Media Used for the Detection of Heated Bacterial Spores. Nature 157, 337 (1946).

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