BACILLUS CO LI COMMUNIS 69 



be set up, in the exudation of which streptococci will occur in 

 large numbers. 



Metliod of staining. — Gram's method is the most satisfactory. 

 Next to Gram's method the most useful is Loffler's blue. It may 

 be noted that most of the putrefactive organisms do not hold 

 Gram's stain. 



Bacillus coli communis— 



{a) Dilute the milk to be examined 500 or 1000 times. Take 

 a sterilised brush, dip it in the dilution, and brush over the surface 

 of six agar plates without recharging the brush. Incubate at 

 42" C, and subculture the coliform colonies (bouillon, milk, litmus 

 milk, gelatine " shake " cultures, etc.). 



{])) Take six tubes of phenol bouillon (005 per cent, of carbolic 

 acid), and inoculate them with crude or diluted milk. Those which 

 show abundant turbidity after twenty-four to forty-eight hours at 

 37' C. may be plated out on phenol-gelatine, incubated at 20^ C, 

 and the coli colonies subcultured ; or diluted milk may be at once 

 plated out on phenol-gelatine, and colonies subcultured on such 

 media as will show the characteristics of the organisms. 



The main characters of the B. coli group of organisms may be 

 briefly stated here, though particulars will be foundelsewhere in 

 the present volume : — (i) They are non-sporing and non-liquefy- 

 ing ; (2) they rarely stain by Gram's method ; (3) they are motile ; 

 (4) they produce acid and gas in glucose and lactose media ; (5) 

 they produce acid in milk, and usually coagulate it ; (6) they grow 

 well at a temperature of 42° C. Referring to the isolation of B. 

 coli Houston writes : " No test based on observation of a change 

 or changes produced in the nutrient medium, and supposed to be 

 characteristic of B. coli, can compare with isolation from plate 

 cultivations of the microbes suspected to be B. coli, and the 

 subsequent attentive study of the biological characters of pure 

 cultures of these bacteria grown in various media." ^ 



Bacillus enteritidis sporogenes of Klein- 

 Take six tubes containing 15 c.c. of fresh milk and sterilise 

 them by boiling for half an hour. Rapidly cool them by plac- 

 ing them in a beaker of cold water, add to each tube i c.c of 

 a I in 500 dilution of the milk to be examined, or if it be preferred 

 o-i c.c. of the crude milk. Heat the inoculated tubes at 80' C. 

 for fifteen minutes. Then remove and cool, and place in Buchner 

 ^ Second Report of Royal Commission on Sewage Disposal^ 190^1 P- 4ii- 



