ISOLATION OF ANAEROBES 



451 



IV. To separate sporulating anaerobes from non-sporulating 

 anaerobes and aerobes 



Heat as described on page 448. 



V. To separate sporulating anaerobes from other sporulating 

 anaerobes by cultural methods 



I. Heating. The following diagram shows how heating may be 

 employed : 



ANAEROBIC BACTERIA 



Early sporulating species 

 (18-24 hours) 



Later sporulating species 

 (24-48 hours) 



Late sporulating species (48 

 hours on) 



PROTEOLYTIC GROUP 



Bifermentans group et alii. 

 Do not occur very fre- 

 quently 



Sporogenes group et alii 



Tetanus group, botulinus 

 group, et alii 



NON-PROTEOLYTIC GROUP 



Nearly all sporulat- 

 ing organisms 



This diagram shows that if proteolytic early-sporulating organ- 

 isms are absent, as is frequently the case, a saccharolytic form may 

 be isolated or be rendered relatively far more abundant by heating 

 eighteen to. twenty-four-hour cultures successively. I have had 

 mixtures of B. sporogenes and organisms of the blackleg group 

 that were not pathogenic for guinea-pigs because of the scarcity 

 of B. Chauvoei. Two successive heatings and inoculations made 

 blackleg the predominant organism and the culture was highly 

 pathogenic. This method is also excellent for organisms of the 

 vibrion-septique group and for many non-pathogenic sacchar- 

 olytic bacteria, as well as the early-sporulating proteolytic ones. 



II. Selective media. Isolation methods usually depend on se- 

 curing a predominance of the organism sought. To increase the 

 relative numbers of an organism with whose nature one is familiar, 

 a medium should be selected on which the organism grows best. 

 For saccharolytic species mixed with proteolytic ones, use sugar- 

 containing media. Meat medium plus 1 per cent glucose is 



