154 DIFGO MANUAL 



coagulase production, violently shake the colonies emulsified in Brain Heart In- 

 fusion for 15 minutes. Add 0.2 ml. of Bacto-Coagulase Plasma Solution. Incubate 

 at 37°C. for one hour. Most coagulase positive staphylococci will form a clot 

 within one hour; however, readings should be made after 2 and 3 hours incuba- 

 tion before being considered as negative. A complete discussion of Bacto-Co- 

 agulase Plasma is given on page 330. 



Newman,^ in a study of the detection of food poisoning attributable to dairy 

 products, used Chapman Stone Medium and Staphylococcus Medium No. 110 

 for the isolation of staphylococci. The coagulase test was run to assist in the 

 detection of pathogenic staphylococci. The cultures for the performance of the 

 coagulase test were grown in Brain Heart Infusion. 



To rehydrate the medium, suspend 20.2 grams of Bacto-Chapman Stone 

 Medium in 100 ml. cold distilled water and heat to boiling to dissolve the 

 medium completely. Distribute in tubes or flasks and sterilize in the autoclave 

 for 10 minutes at 15 pounds pressure (121°C.). For field work, or if the medium 

 is to be inoculated the same day as prepared, sterilization in the autoclave may 

 be omitted, heating the medium to effect complete solution is sufficient. Pour into 

 plates while the medium is hot, avoiding formation of bubbles. The medium 

 after solidification should be opaque and white. Final reaction of the medium will 

 be pH 7.0. 



One pound of Bacto-Chapman Stone Medium will make 2.2 liters of medium. 



1 Food Research, 13:100:1948. 



* J. Milk and Food Tech., 13:226:1950. 



BACTO 



MITIS SALIVARIUS AGAR (B298) 



DEHYDRATED 



Bacto-Tr>'ptose 10 g 



Proteose Peptone No. 3, Difco . 5 g, 



Proteose Peptone, Difco 5 g 



Bacto-Dextrose 1 g 



Saccharose, Difco 50 g 



Dipotassium Phosphate 4 g 



Trypan Blue - 0.075 g 



Bacto-Crystal Violet 0.0008 g 



Bacto-Agar 15g 



Bacto-Mitis Salivarius Agar is prepared according to the formula described by 

 Chapman^'- for the isolation of Streptococcus mitis, S. salivarius and enterococci. 

 Some bacteriologists refer to these organisms as "Streptococcus viridans" and 

 "nonhemolytic streptococci," respectively, because of their alpha and gamma 

 hemolysis on Blood Agar prepared from Bacto-Heart Infusion Agar or Bacto- 

 Tryptose Blood Agar Base. The final medium, containing Bacto-Chapman Tel- 

 lurite Solution, is highly selective for these organisms, making possible their isola- 

 tion from grossly contaminated specimens such as feces or exudates from 

 different body cavities. 



Different methods have been employed for the isolation of streptococci and 

 enterococci from mixed cultures. Snyder and Lichstein^ and Lichstein and Sny- 

 der* used sodium azide as inhibiting agents for Gram-negative bacteria including 

 proteus. Chapman^ described a Tellurite Medium and an Azide Medium for 

 isolation of S. salivarius and S. mitis. 



Chapman,^'2 continuing his studies, reported a complete and detailed method 

 for the isolation and testing for the pathogenicity of fecal streptococci. Decimal 



