A Simple and Practical Medium for Differentiating B. Typhosus, B. Paratyphosus A., B. Paratyphosus B., B. Enteritidis, and B. Coli

Abstract

Before the war in Europe began paratyphoid fever was relatively rare, but owing partly to prophylactic inoculation against typhoid, it soon became more common among soldiers than the latter disease. With increased prevalence there is need of simple cultural tests for the recognition of the causative organisms. A number of such tests have been devised. Russell's double sugar medium, consisting of litmus agar with 1 per cent lactose and 0.1 per cent glucose, is widely used to receive the fishings of suspicious colonies. It differentiates the paratyphoids and B. enteritidis from B. typhomus and the B. coli group, but does not differentiate between B. paratypho&su A, B. paratyphosus B., and B. enterilidis. To determine which of these latter organisms is present, further inoculation of the culture into litmus milk, lead acetate agar, or other special culture media, and agglutination tests must be resorted to.It occurred to me that by pouring one agar medium into a test tube and allowing the agar to solidify, and then pouring a layer of a second differential agar medium upon this, a medium would be obtained which would furnish, in twenty four hours, more information from a stab fishing than do the media at present employed. Of a large number of such combinations, the following proved to be the most satisfactory.Meat infusion agar is prepared in the usual way, cleared with egg-white, and titrated while hot to about -0.2 to -0.4 with phenolphthalein as an indicator. A 2 per cent solution of neu-19 on July 31, 2020 by guest