MATERIAL FROM THE LIVING SUBJECT 231 



established. The isolation of streptococci from intestinal contents 

 is made either by direct plating upon dextrose agar, or by inoculation 

 of feces into dextrose broth. The streptococcus, as a general rule, 

 produces enough acid in the medium after one or two days' growth 

 at body temperature to seriously restrain the development of the 

 intestinal bacteria. A Gram stain prepared from the sediment of the 

 fermentation tube will frequently reveal a nearly pure culture of the 

 organism. A direct smear from the feces, stained by Gram's method, 

 also will indicate the unusual preponderance of streptococci in acute 

 streptococcus enteritis. 



The members of the alcaligenes, dysentery, typhoid, paratyphoid 

 group comprise the more important bacilli ordinarily sought for in 

 the intestinal contents. Their isolation upon ordinary media is diffi- 

 cult because Bacillus coli, the most important of the intestinal organ- 

 isms, greatly outnumbers the more delicate pathogenic bacteria; its 

 colonies on ordinary media are not readily distinguished from typhoid 

 colonies. The Endo medium (see page 201) however, affords a ready 

 means of identification between the pathogenic bacteria and Bacillus 

 coli. The Endo medium is essentially lactose agar containing a small 

 amount of basic fuchsin decolorized with sodium sulphite. Organic 

 acids including lactic acid restore the color to fuchsin. None of the 

 members of the Alcaligenes-typhoid Group ferment lactose, therefore 

 no lactic acid is formed in and around colonies of these bacilli. Bacillus 

 coli, on the other hand, ferments lactose, and consequently the colonies 

 of this organism are colored red. The lactic acid resulting from the 

 fermentation of the lactose locally restores the color to the fuchsin. 



Procedure. A thin suspension in plain broth, prepared from a freshly 

 passed specimen of feces, is incubated if possible, for an hour at 37 

 C., then rubbed gently over the surface of an Endo plate with a sterile 

 bent-glass rod or platinum needle. At the end of eighteen to twenty- 

 four hours, small colorless transparent colonies are removed to 0.1 

 per cent, dextrose meat infusion broth for further development. 

 Inasmuch as colonies of B. alcaligenes, dysenteric (Flexner, Shiga 

 and other strains) typhosus, paratyphosus alpha and beta, and the 

 Morgan bacillus are practically identical in appearance, a final iden- 

 tification must depend upon their cultural characteristics (see page 

 316 for table) and their agglutination with specific sera of high potency. 



Members of the Mucosus Capsulatus Group are occasionally found 

 in acute and subacute diarrheas. They grow readily upon the surface 

 of Endo plates as very viscid, slimy colonies which are readily recog- 



