The Action of Dysentery Bacilli on Nitrites and Nitrates

Abstract

(1) Dysentery strains from various sources have been examined with respect to their power of reducing nitrates to nitrites and of further destroying nitrites. All the strains with one exception (B. Neisser Ac.) reduced nitrates to nitrites. None of the strains which fail to ferment mannite (Shiga type) destroyed nitrites. Those dysentery strains which form acid from mannite differ amongst themselves in regard to their action on sugars and also in their effect on nitrites. Of the eight mannite-fermenting strains examined, two (B. dysenteriae Jürgens and B. Neisser Nc.) failed to destroy nitrites.(2) B. dysenteriae Jürgens, although closely related to B. dysenteriae Flexner, differs from it both in its action on litmus-whey and in failing to destroy nitrite. It must therefore be considered a different strain. B. dysenteriae Jürgens is remarkable as being the only one of the strains examined which forms indol and at the same time fails to destory nitrites. It is consequently the only one which gives the cholera-red reaction.(3) The addition of glucose (i.e. of a carbohydrate from which acid can be formed) enables Shiga strains to destroy nitrite.(4) In the presence of an abundant supply of oxygen all the strains fail to destroy nitrites and nitrates.(5) In glucose-containing media the inhibitory effect of oxygen is less marked.(6) Under anaerobic conditions Shiga strains and B. dysenteriae Jiirgens still fail to destroy nitrites.