APPENDIX B 

 HANDLING STOCK CULTURES 



Those in charge of a bacteriological laboratory will have need of 

 stock cultures of the organisms commonly used. These cultures may 

 be obtained from isolations made at the laboratory or may be obtained 

 from other laboratories. In America bacteriologists obtain many of 

 their cultures from fellow bacteriologists and also from such institu- 

 tions as the laboratory of the American Museum of Natural History, 

 and the firm of Parke, Davis and Co. of Detroit. In Europe Krai's 

 laboratory in Prag is a convenient and prompt source of supply. 



It should always be remembered that mistakes sometimes occur, 

 and that contaminations are liable in transit. Therefore a culture 

 received from another source should be cultivated for a time on media 

 which will demonstrate its critical characters, before it finds its place 

 in the collection of stock cultures. 



The standard beef-peptone agar appears to be best suited for stock 

 cultures of most organisms. It is put into rather large test tubes 18 

 by 175 mm., which are carefully plugged with deep plugs and slanted 

 after sterilization. 



After inoculation the tubes should be kept in a cool, dry place 

 where there is not much fluctuation of temperature. A special room 

 should be constructed where possible. It should not be built against 

 an outside wall and should be entered by one tightly closing door. 

 The room should contain plain cupboards which can easily be cleaned 

 and are closed by tightly fitting doors. The cupboard shelves should 

 be far enough apart so that the cotton plugs will not rub the shelf 

 above as they are removed from the cupboard. 



Transfers to newly prepared sterile tubes of media should be made 

 every six or eight weeks. The length of time that a culture retains 

 its vitality depends largely upon the temperature at which it is kept. 

 If it is kept between 10 and 15 C., transfers once in ten to twelve 

 weeks may suffice. 



The old cultures should in every case be kept until one is certain 

 that the transfer has grown and is pure. If contaminations appear, 

 one may go back to the old culture and pour plates in order to 

 reisolate pure cultures. 



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