PRINCIPLES CONCERNING THE ISOLATION OF 



ANAEROBES 



STUDIES IN PATHOGENIC ANAEROBES. II 



HILDA HEMPL HELLER 



From the George Williams Hooper Foundation for Medical Research, University of 

 California Medical School, San Francisco 



Received for publication December 30, 1920 



The subject of the isolation of anaerobes is one which the worker 

 is inclined to approach with apologies. Every month or so a 

 paper appears in some journal in which a new and expeditious 

 procedure for the separation of anaerobes is described. There 

 are many successful ways of isolating anaerobes and it is unwise 

 to recommend any one method above all others. I have succeeded 

 with various arrangements; and wish in this paper to analyze 

 some of the principles governing the isolation of these organisms 

 and to explain a few of the pitfalls which have caused many 

 workers to believe that the securing of "absolutely pure" anae- 

 robic cultures is a difficult matter. With a little practice and with 

 the exercise of much discrimination, anaerobes may be isolated 

 as quickly, or nearly as quickly, as aerobes. 



Contamination occurs somewhat more frequently in anaerobic 

 cultures than in those of aerobes. Contamination of originally 

 pure cultures may be attributed to the following causes: (1) In- 

 sufficiently sterilized media; anaerobe media are usually pasty 

 and require more careful sterilization than others. (2) Inocu- 

 lation transfer involving the exposure of the cotton plug and of 

 the inoculum to the air. I have noted in working in London and 

 near the sea in San Francisco, that the more dusty the air, the 

 more frequent are contaminations, and the contamination 

 flora may vary according to location. (3) During incubation in 

 closed jars the cotton plugs may become sufficiently moist for 



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