298 DIFCO MANUAL 



the oxidation-reduction potential with Kitchen's^ method of adding 0.05 to 0.1 

 per cent agar to the medium for the growth of anaerobes. Such a combination 

 was found particularly useful as a sterility test medium for biological containing 

 mercurial preservatives, since the sodium thioglycollate neutralizes the toxic 

 effect of any mercurial carried over with the inoculum, while the agar provides 

 anaerobic conditions necessary for growth. 



Since sodium thioglycollate is toxic for some organisms, especially with inocula 

 containing very few organisms, it is recommended that no more of the sodium 

 thioglycollate be added to the medium than is required for mercurial neutraliza- 

 tion. Sodium thioglycollate in 0.05 per cent concentration is specified in the 

 thioglycollate media of the National Institute of Health^ for sterility testing. 

 These media are discussed under Bacto-Fluid Thioglycollate Medium and Bacto- 

 N.I.H. Thioglycollate Broth on pages 195 and 198. Bacto-Brewer Anaerobic 

 Agar, discussed on page 126, contains sodium thioglycollate, and is employed 

 as a solid medium for the cultivation of anaerobes. 



1 Centr. Bakt. I Abt., 23:1038:1898. ^ J. Infectious Diseases, 29:390:1921. 



2 Biochem. J., 20:1125:1926. ^National Institute of Health Circular: Culture 

 8 J. Bact., 39:10:1940. Media for Sterility Test, 2nd Revision, Feb. 5, 



-J. isact., 39:10:1940. 



* J. Am. Med. Assoc, 115:598:1940 



1946. 



THIOGLYGOLLIG ACID, DIFCO (B250) 



Thioglycollic Acid, Difco is recommended for use in media designed for the 

 cultivation of organisms in the presence of mercurial salt preservative. It may 

 also be used for the preparation of media of a low Eh. In the preparation of 

 media for the sterility testing of biologicals, thioglycollic acid or sodium thiogly- 

 collate may be employed. A complete discussion of these media is given under 

 Bacto-Fluid Thioglycollate Medium page 195 and Bacto-N.I.H. Thioglycollate 

 Broth page 198. 



UREA, DIFCO (B190) 



Urea, Difco is purified urea recommended for the preparation of bacterio- 

 logical culture media. The ability of an organism to hydrolyze urea is often a 

 salient characteristic in its identification. The use of Urea Broth and Urea Agar 

 Base for the identification of enteric organisms is discussed in detail on pages 

 170 and 171. 



POTASSIUM TELLURITE, DIFCO (B384) 



Potassium Tellurite, Difco is recommended for use as a selective agent in 

 media for the isolation and differentiation of diphtheria bacilli. It has also 

 been used as a selective agent in media designed for isolation of streptococci 

 and the enrichment and isolation of pleuropneumonia-like organisms. Potassium 

 Tellurite, Difco is readily soluble and well suited for use in media requiring this 

 chemical, as each batch is checked to determine its inhibitive properties. Bacto- 

 Chapman Tellurite Solution as discussed on page 277 is prepared with Potassium 

 Tellurite. A complete description of the media using this selective agent is given 

 under Bacto-PPLO Enrichment Broth, page 82 and Mitis Salivarius Agar, 

 page 154. 



