296 



DIFGO MANUAL 



Color 

 pH Range Acid Alkali 



Preparation 



Methyl Red (B207) . . . . 4.4-6.0 Red-Yellow 



Neutral Red (B208) 



6.8- 8.0 Red-Yellow 



Litmus, Pure (B209) .... 4.5- 8.3 Red-Blue 

 Phenolphthalein (B210) . 8.3-10.0 Colorless-Red 



0.1 g. in 300 ml. ethanol 

 and dilute to 500 ml. 

 with distilled water 



0.1 g. in 60 ml. ethanol 

 make up to 100 ml. 



LO g. in 100 ml. water 



1.0 g. in 60 ml. ethanol 

 and make up to 100 

 ml. with ethanol. 



BIOCHEMICALS 



i>-AMINOBENZOIG ACID, DIFGO (B240) 



/?-Aminobenzoic acid is recommended for use in liquid culture media for the 

 prevention of bacterial stasis due to any sulfonamide drug. It should be added to 

 all liquid media used for blood cultures of patients under sulfonamide therapy, 

 and in the culture of exudates or other materials containing sulfonamide com- 

 pounds. As pointed out by Lockwood^ and McLeod^ most culture media nor- 

 mally contain some sulfonamide inhibitors which generally are not sufficient 

 to neutralize completely the sulfonamides likely to be encountered. The addition 

 of 5 mg. of p-aminobenzoic acid to 100 ml. of medium will more than suffice 

 to neutralize the bacteriostatic effect of 1.5 mg. per cent sulfonamide drug. This 

 quantity of p-aminobenzoic acid is not toxic to fastidious pathogens even though 

 the inocula contain only a few organisms. The report of Janeway^ shows the 

 value of p-aminobenzoic acid in culture media wherever sulfonamides are en- 

 countered. 



1 J. Immunol., 35- 155:1938. 



2 J. Exp. Med., 72:217:1940. 



8 J. Am. Med. Assoc, 116:941:1941 



i>.AMINODIMETHYLANILINE MONOHYDRO- 



CHLORIDE, DIFGO (B249) 



/?-Aminodimethylaniline Monohydrochloride, Difco (dimethyl-p-phenylene- 

 diamine hydrochloride) is recommended for use in the detection of oxidase 

 production by microorganisms. Its practical application in the bacteriological 

 laboratory was first described by Gordon and McLeod^ who employed this 

 reagent as an aid in differentiating colonies of oxidase-producing microorganisms 

 from those not elaborating this enzyme. These authors found the oxidase test to 

 be particularly helpful in the detection of Neisseria gonorrhoeae colonies growing 

 among colonies of extraneous organisms in the primary culture of gonococcal 

 exudates on Chocolate Agar. Since its introduction for this purpose p-amino- 

 dimethylaniline monohydrochloride has been widely adopted for use in the 

 cultural diagnosis of gonorrhoea. ^'^ Oxidase positive colonies flooded or sprayed 

 with p-aminodimethylaniline monohydrochloride turn pink within a minute or 



