DIAGNOSIS OF CHOLERA 541 



straight platinum needle and mix with a drop of a 1/200 dilution 

 cholera serum of high titre (1 in 5-10,000). If agglutination be 

 positive the remainder of the colony is picked off the plate and 

 transferred to an agar or peptone water tube for further growth 

 and examination is necessary. 



(In many instances it is not necessary to proceed beyond the 

 peptone water culture referred to in (ft), and it is occasionally 

 possible to isolate with ease the vibrio from plates prepared directly 

 from the stool. The stained films and hanging drops prepared at 

 the specified times give an indication as to the number (if any) 

 of vibrios present at that particular time, and plates are made 

 immediately they are found to be fairly numerous, the routine 

 being designed to complete the examination in the shortest 

 possible time. ) * 



A better medium to employ for plating is Dieudonne's blood 

 alkali agar. Equal parts of defibrinated ox-blood and normal 

 caustic potash solution are mixed and sterilised in the steamer. Of 

 this 30 c.c. are mixed with 70 c.c. of 3 per cent, peptone-agar 

 (neutral to litmus), previously melted. Plates are poured and kept 

 at 60 C. for half an hour, and are then allowed to stand for forty- 

 eight hours for ammonia to evaporate. On this medium few 

 organisms except the cholera vibrio develop (but cholera-like 

 vibrios develop equally well). 



The Dieudonne medium requires fresh blood, but Lentz has 

 devised a dry blood-alkali powder for its preparation. Freshly 

 obtained and defibrinated ox-blood is mixed with an equal 

 quantity of normal caustic potash solution. The mixture is 

 steamed for half -an -hour and the fluid is then evaporated to 

 dryness in vacuo over sulphuric acid at 37 C. The dry mass is 

 finely powdered and preserved in a stoppered bottle. For use 

 3 grm. of the powder are dissolved in 30 c.c. of distilled water 

 and the solution is mixed with 70 c.c. of melted neutral agar 

 as above, and plates are poured and are ready for immediate 

 use. 



3. If the case has lasted some days, the agglutination reaction 

 may be applied, testing the patient's serum on a known strain of 

 cholera vibrio. 



1 The writer is indebted to Mr. Edwin Burgess, of the Bacteriological 

 Institute, Colombo, for the foregoing technique. 



