100 DIFCO MANUAL 



Standard Methods Committee of the American Public Health Association, when 

 in 1917^ they specified the use of beef extract rather than infusion of fresh meat 

 for use in the preparation of media for the examination of water. In 1921 

 "Standard Methods for Milk Analysis,"^ in the interests of greater uniformity, 

 specified the use of beef extract rather than infusions of beef for media used in 

 plate counts of milk. A standard medium must be uniform in composition and 

 easily prepared. Any procedure that simplifies the preparation and maintains 

 greater uniformity of composition of media is a definite advance in technical 

 bacteriology. 



For isolation or cultivation of strains of many highly pathogenic organisms 

 such as the Brucella, streptococci, pneumococci, gonococci, meningococci and 

 others, it has generally been considered necessary to have infusions of fresh meat 

 in the medium. Bateriological peptones have been pioneered and developed by 

 Difco Laboratories that make the addition of infusions of fresh meat unnecessary 

 for the cultivation of many organisms, including even the discriminating gono- 

 cocci, meningococci, pneumococci, streptococci. Brucella and others. For example, 

 Bacto-Tryptose Agar, developed and prepared in 1938, proved more satisfactory 

 for the isolation and cultivation of Brucella, streptococci and pneumococci than 

 previously employed infusion media. Bacto-Proteose No. 3 Agar and Bacto- 

 Dextrose Starch Agar also developed in 1938 for the isolation and cultivation of 

 the gonococci, simplified the cultural diagnosis of gonorrhoea so as to make it a 

 routine test even for the smallest laboratory. These media contain specially 

 prepared bacteriological peptones without infusions and have proven in many 

 years of practical use to be superior to previously recommended complicated 

 infusion and enriched media used for the cultivation of these organisms. A 2 per 

 cent solution of Bacto-Tryptose or Proteose Peptone No. 3 will satisfactorily 

 replace the peptone-infusion portion of media previously employed for the 

 isolation and propagation of streptococci, pneumococci, meningococci, gonococci 

 and other fastidious microorganisms. In the discussion of Meat Infusion Broths 

 in "Diagnostic Procedures and Reagents"^ of the American Public Health As- 

 sociation, the referee states that in his laboratory a broth with 2 per cent pan- 

 creatic digest of casein and 0.5 per cent yeast extract has been substituted for 

 infusion broth and the growth of the more fastidious organisms has been heavier 

 than that obtained in infusion media. 



The simplicity of preparation and uniformity of composition, combined with 

 the ability to grow the organisms, make the Peptone Media listed in this secton 

 of practical value and interest. 



It is a well recognized fact that infusion media contain varying amounts of 

 muscle sugar. In preparing media from peptones this variability can be controlled 

 by the addition of a known and definite quantity of dextrose. A small quantity 

 of dextrose (0.025-0.05 per cent) in peptone media assists materially in the 

 initiation of growth of many bacteria. 



1 Standard Methods of Water Analysis, ^ Diagnostic Procedures and Reagents, 



3rd Edition: 93: 191 7. 3rd Edition: 13: 1950. 



" Standard Methods of Milk Analysis, 

 3rd Edition: 7: 192 1. 



BACTO 



TRYPTOSE PHOSPHATE BROTH (B60) 



DEHYDRATED 



Bacto-Tryptose 20 g. 



Bacto-Dextrose 2 g. 



Sodium Chloride 5 g. 



Disodium Phosphate 2.5 g. 



