Viability of Dysentery, Enteric and Cholera Organisms in Milk Curd (Dahi) *The paper was read before the Indian Science Congress Association held at Nagpur in January 1945. †Rearranged by Editor.

S. K. GHOSH, b.sc. Assistant Chemist (From the Department of Bacteriology and Pathology, School of Tropical Medicine, Calcutta) In Calcutta, large quantities of milk curd (dahi) are consumed as food especially in feasts. It is prepared by vendors in open earthen pots, and sometimes kept for two or more days before it is consumed; there is the possibility of its being contaminated with dysentery, enteric and cholera organisms. Twenty-seven samples of curd, 16 ' sweet' and 11 ' sourwere bought from different shops in Calcutta for testing. Smears showed lactobacilli in all of them. Their pH, determined by colorimeter method, ranged from 4.2 to 4.7. Viability tests Four drops of the culture of the above three organisms were separately added to about 10 c.cm. of curd before and after neutralization with caustic soda at room temperature, and subcultures were made every 5, 10, 15, 30 and 60 minutes and 2, 3 and 20 hours. (1) Viability of V. cholera, Inaba and Ogawa subtypes mixed Nine samples were tested with this mixture and the results obtained with four specimens are given in the table. The results were the same in other samples. It will be seen from the table that cholera vibrios are completely killed within 5 minutes by sweet as well as sour dalii. After neutralization of the curd, when the pH becomes about 7.2, its killing power is lost. (2) Viability of Bad. typhosum All the 27 samples were tested with this organism and the results are given in the following table :?