DEHYDRATED CULTURE MEDIA 151 



at 15 pounds pressure (121°C.). The final reaction of the medium will be 

 pH 7.4. 



One pound of Bacto-Mannitol Salt Agar will make 4.0 liters of medium. 



1 J. Bact., 50:201:1945. 3 Am. J. Vet. Res., 8:173:1947. 



aZentr. Bakt., I Abt. Orig., 149:122:1942. * Am. J. Vet. Res., 8:275:1947. 



BACTO 



STAPHYLOCOCCUS MEDIUM NO. 110 (B297) 



DEHYDRATED 



Bacto- Yeast Extract 2.5 g 



Bacto-TryTDtone 10 g 



Bacto-Gelatin 30 g, 



Bacto-Lactose 2 g. 



J-Mannitol, Difco 10 g, 



Sodium Chloride 75 g. 



Dipotassium Phosphate 5 g 



Bacto-Agar 15 g 



Bacto-Staphylococcus Medium No. 110 is a selective medium for the isolation 

 of staphylococci. In addition, pigment and coagulase production, Stone's method 

 for liquefaction of gelatin and fermentation of mannitol may be determined 

 directly on this medium without the necessity of making transplants for these 

 conformity tests. These characteristics, and the selective properties of the medium 

 due to its high sodium chloride content, make it of particular value for the 

 isolation of staphylococci, especially those suspected of being pathogenic or in- 

 volved in cases of food poisoning. The medium has the additional advantage 

 that, with few exceptions, pathogenic strains produce typical orange pigmented 

 colonies whereas nonpathogenic types produce white colonies, a relationship that 

 is not obtained on any other medium. The coagulase test should be made using 

 a subculture of the suspected colony in Brain Heart Infusion or a Brain Heart 

 Infusion suspension of the organism grown on Heart Infusion Agar slants. 



Koch^ reported that staphylococci were not inhibited by a concentration of 

 7.5 per cent sodium chloride in solid niedia. Chapman^ noted that most bacteria, 

 other than staphylococci, were inhibited on such media and that pathogenic 

 staphylococci grew more luxuriantly than did nonpathogenic strains. He suggested 

 that 7.5 per cent sodium chloride be added to Bacto-Phenol Red Mannitol Agar 

 as a selective isolation medium for staphylococci. In a study of the resistance of 

 chronic staphylococcal bovine mastitis to massive penicillin therapy McCulloch^ 

 stated that the staphylococci responsible for the mastitis grew well and formed 

 acid on Bacto-Phenol Red Mannitol Agar to which 7.0 per cent sodium chloride 

 had been added. Stone* described a culture medium on which food poisoning 

 staphylococci gave a gelatinase test, or were "Stone reaction" positive. Chapman, 

 Lieb and Curcio^ pointed out the nonspecificity of this single test and reported 

 that in addition to being "Stone reaction" positive, typical food poisoning 

 staphylococci must produce pigment, coagulate plasma, hemolyze rabbit blood 

 and ferment mannitol. 



Continued study of the isolation of staphylococci by Chapman^ led to the 

 development of a medium designated as Staphylococcus Medium No. 110. In 

 addition to being selective for staphylococci due to the high sodium chloride 

 content, this medium is well suited for pigment formation, may be used for the 

 determination of the fermentation of mannitol, for the Stone type gelatinase test 

 and gives a growth satisfactory for the coagulase test. According to Chapman^ 



