DIAGNOSIS 



1811 



colony developing should be further examined and the gerrn 

 investigated as regards the following characters: — 



(a) Motility.— The cholera vibrio is very actively motile. 



{b) Morphology. — The cholera organism is often bent, comma-hke, 

 but may be straight, bacillus-hke. 



(c) Agglutination. — A strong anticholera serum obtained from 

 some well-known laboratory should be used. Any vibrio found 

 in stools which is agglutinated by this serum in a dilution not less 

 than I in 2,000 can safely be considered, as a rule, to be the true 

 germ of cholera. In doubtful cases, all the cultural characters 

 should be studied, and Pfeiffer's test and Castellani's absorption 

 test should be carried out. - 



Dunbar has recommended a special agglutinative test, which consists in 

 mixing directly a drop of the stools with diluted immune serum. The cholera 

 vibrios become agglutinated. This process is practicable only when the stools 

 contain many vibrios. 



3. Take a rice-hke flake, and smear it direct on to the surface of 

 MacConkey's lactose-agar plate, using a sterile bent glass rod or 

 Kruse's platinum pencil. Inoculate with the same rod. or pencil 

 without recharging the surface of two more plates, and. incubate at 

 35° C. The colonies of the cholera and cholera-hke vibrios develop 

 on MacConkey's medium as delicate, small, yellowish, roundish dots 

 within txvelve to eighteen hours. Any suspicious yellowish colony 

 should ,be examined, and the germ investigated as regards 

 motility, morphology, and agglutination, as already mentioned. 



4. Inoculate the surface of three ordinary serum-tubes with the 

 suspected stools, and incubate at 35° C. If within sixteen hours 

 there is no zone of liquefaction in the medium, cholera may be practi- 

 cally excluded. If there is liquefaction, this may be due to the 

 presence of the cholera or other serum-liquefying germs, or to the 

 stools containing an amount of proteolytic substances. The liquefied 

 serum may be plated on MacConkey or ordinary agar platps, and 

 any suspicious colony further investigated. 



5. Dieudonne's special strongly alkaline blood agar may be used 

 for the isolation of the cholera, vibrio in faeces. On this medium 

 the cholera germ grows well, .forming pearl-like colonies, while the, 

 coli and coli-like organisms scarcely vegetate. Of course, the colpnie^ 

 which grow must be carefully investigated, as already described. 



6. Bandi's Method— The suspected faecal matter is inoculated into a 

 sedimentative tube containing peptone water and a certain amount of immune 

 serum. After incubation at 37° C. for three to seven hours this tube showsi 

 if the case is one of cholera, numerous small floccuU, which at first are in 

 suspension, and later sink to the bottom. These floccuH consist of 8 gglutinated 

 vibrios. ' 



7. Ottolenghi's Method.— -The suspected stools are inoculated in a medium 

 consisting of pure bile mixed with 3 per cent, of a 10 per cent, solution of 

 sodium carbonate, which after incubation at 37° C. for some hours is plated 

 and further investigated. 



8. Aronson's Method. — This is an alkaline agar medium containing cane 

 sugar and dextrin, with fuchsin and sodium sulphite as indicator. Good 

 results have been recorded by several observers. 



