DEHYDRATED CULTURE MEDIA 149 



One pound of Bacto-Dextrose Proteose No. 3 Agar will make 11.3 liters of 

 medium. 



1 Muench. Wochschr., 59:1652:1912. ^ J. Infectious Diseases, 59:22:1936. 



2 Zentr. Bakt., 114:539:1929. ''J. Infectious Diseases, 60:09:1937. 

 Path. Bact., 34:667:1931. « Am. J. Pub. Health., 29:064:1959. 



■i 



Hyg., 32:544:1932. ® J- Hyg., 37:552: i937- 



Path. Bact., 38:114:1934. 



BACTO 



MUELLER TELLURITE BASE (B264) 



DEHYDRATED 



Bacto-Casamino Acids, Technical . . 20 g. 



Casein 5 g. 



/-Tryptophane 0.05 g. 



Potassium Dihydrogen Phosphate . . 0.3 g. 



Magnesium Sulfate 0.1 g. 



Bacto-Agar 20 g. 



Bacto-Mueller Tellurite Base enriched with Bacto-Mueller Tellurite Serum is 

 recommended for the isolation, differentiation and identification of Corynebac- 

 terium diphtheriae. The basal medium and sterile enrichment are prepared ac- 

 cording to the formula given by Mueller and Miller.^ 



Many selective media containing tellurite have been described for the initial 

 cultivation of members of the Corynebacterium group. The medium as described 

 by Mueller and Miller is transparent, requires no heating following the addition 

 of the sterile tellurite enrichment, and may be prepared from standardized ma- 

 terials to give a uniform desired growth response. The availability of the compo- 

 nents of the medium in the form of the dehydrated base and sterilized enrich- 

 ment is pointed out by the authors making the preparation of the final medium 

 containing all the nutriments required by the Corynebacterium group and of the 

 correct selectivity an easy task. A discussion of Bacto-Mueller Tellurite Serum, 

 the enrichment used in preparing the transparent medium, is described on page 

 278. 



The presence or absence of organisms consistent with the morphological char- 

 acteristics of C. diphtheriae in a suspected diphtheria case materially assists the 

 physician in making an accurate diagnosis. This medium was developed after 4 

 years of practical use of tellurite plate media in the detection of diphtheria 

 carriers. It has given excellent results in other laboratories in detecting diphtheria 

 organisms. It permits a differentiation of the mitis, gravis and intermedins types. 

 As described by Mueller and Miller easily visible confluent growth of either mitis 

 or gravis types of C. diphtheriae is obtained from a fresh case after 15-18 hours 

 incubation. Plates showing no growth should be incubated for an additional 24 

 hours. In 48 hours mitis colonies are 1.0-1.5 mm. in diameter, black and convex 

 with a glistening surface. Gravis types in contrast show flat irregular colonies with 

 a dull surface, slate gray in color and 2-3 mm. in diameter. Gravis types seldom 

 show typical "daisy head" colonies. The size of the colony and degree of darken- 

 ing increases with length of incubation. Intermedins colonies are pin point in 

 size in 24 hours and approximately 0.2-0.3 mm. in diameter after 48 hours incu- 

 bation. The colonies show little darkening but appear brownish gray with a white 

 background in a good light. Hoffman's bacillus and other diphtheroids grow on 

 the medium, often resembling mitis types. Cocci, non-diphtheroid bacilli and 

 yeast are generally inhibited. Cocci, when they do produce colonies, resemble 

 mitis types. Colonies or growth suggestive of diphtheria bacilli should be ex- 



