Action of Bacilli of Paratyphoid,Dysentery and Metadysentery Groups on Various Starches.

Abstract

The action of certain bacteria on potato starch has been studied, but very little is known on the action of bacteria on the less common starches. For some time I have carried out researches on the action of bacilli of the paratyphoid, dysentery and metadysentery groups on various starches, and on the possibility of using starch reactions in the differentiation of organisms of these groups.

Fifteen starches have been used, viz., arrowroot, barley, bean, canna, corn, ginger, lentil, oat, pea, potato, rice, sago, tapioca, yam, wheat. The so-called soluble forms have been used, but solution is seldom complete.∗

Technique. Tubes containing 1 per cent solution of the various starches in peptone water are used, each tube containing a Durham's

fermentation tube, or saccharymeters may be used. It must be noted that many starches do not dissolve completely. The tubes are inoculated with the different organisms and placed in the incubator at 37° for 21 days, readings being taken on the 7th day, the 14th day and the 21st day.

I suggested some years ago the term “metadysentery bacilli” to denote a group of bacilli capable of producing dysenteric symptoms in man but culturally different from the true dysentery bacilli (Shiga-Kruse, Flexner, Hiss-Russell). These bacilli are characterized by the following features:

1 Like the true dysentery bacilli they do not produce gas in any sugar.

2 In contrast to the true dysentery bacilli they either produce acidity in lactose and clot milk, or produce acidity in lactose without clotting milk, or clot milk without producing acidity in lactose.

There are several species of the metadysentery bacilli which Chalmers and I grouped into two genera: Lankoides (milk clotted), Dysenteroides (milk not clotted). The two principal species are B. ceylonensis A and B. ceylonensis B, and my experiments have been carried out with these two germs; the results are collected in Table III.