DEHYDRATED CULTURE MEDIA 175 



minutes at the interface of the ether and the Ehrlich reagent. Ehrlich reagent 

 consists of 1 gram of ^-dimethylaminobenzaldehyde, 95 ml. ethyl alcohol (95 

 per cent) and 20 ml. of concentrated hydrochloric acid. 



Bacto-S I M Medium is especially recommended as an aid in the routine con- 

 firmation of members of the Salmonella and Shigella groups following presump- 

 tive evidence as obtained on the differential tube media (Russell Double Sugar 

 Agar, Krumwiede Triple Sugar Agar and Triple Sugar Iron Agar) . As with other 

 differential media, it is necessary to use pure cultures for inoculation. Generally, 

 an incubation period of 18-2.4 hours or less is sufficient to give reactions by typi- 

 cal organisms in this group. Occasionally an atypical culture may be encountered 

 which will fail to produce hydrogen sulfide, indole or motility in 18-24 hours 

 incubation. Typical cultural reactions of the pathogenic Gram negative enteric 

 bacteria are: 



S. typhosa Salmonella Shigella 



Motility -|- 4- — 



Hydrogen sulfide -|~ — — 



Indole — — ±: 



To rehydrate the medium, suspend 36 grams Bacto-S I M Medium in 1000 ml. 

 cold distilled water and heat to boiling to dissolve the medium completely. Dis- 

 tribute the medium in tubes to a depth of about 3 inches and sterilize in the 

 autoclave for 15 minutes at 15 pounds pressure (121°C.). The tubes of medium 

 are solidified in a vertical position. Inoculate with a single stab using a straight 

 needle through the center and to a depth of about two-thirds of the medium. 

 Incubate for 18-24 hours at 37 °C. and observe for motility, hydrogen sulfide 

 and indole, as indicated above. Final reaction of the medium will be pH 7.3. 



One pound of Bacto-S I M Medium will make 12.6 liters of medium. 



1 Dissert. St. Petersburg, 1897. 8 Tech. Bull. Reg. Med. Tech., 5:1:1944. 



a J. Infectious Diseases, 21:554:1917. » Rev. Inst. Bact., "Dr. Carlos G. Malbran", 



3 J. Exp. Med., 2:677:1897. 11:286:1943. 



* Zeit. Hyg. Infektionskrank., 58:441:1908. 1° J. Bact., 62:347: 1951. 



s J. Infectious Diseases, 6:194:1909. ii Manual of Methods of Pure Culture Study of 



8 J. Bact., 31:575:1936. Bacteria, Leaflet V, page 6, 7th Editioa, 1939. 



'J. Lab. Clin. Med., 25:649:1940. 



BACTO 



TERGITOL-7 AGAR (B455) 



DEHYDRATED 



Proteose Peptone No. 3, Difco . . 5 g. 



Bacto- Yeast Extract 3 g. 



Bacto-Lactose 10 g. 



Bacto- Agar 15 g. 



Tergitol 7 0.1 ml. 



Bacto Brom Thymol Blue 0.025 g. 



Bacto-Tergitol 7 Agar is a selective medium for Escherichia coli and members 

 of the coliform group, prepared according to the formula given by Chapman.^ 

 Chapman 2,3 reported that the addition of triphenyltetrazolium chloride (TTG) 

 to this medium permitted the confirmation of E. coli after 10 hours incubation, 

 and also that this medium gave excellent results in the cultivation of Monilia 

 and other fungi. 



Chapman^ reported that the addition of Tergitol 7 to an agar medium consist- 

 ing of Proteose Peptone No. 3, Bacto-Yeast Extract, Lactose and Brom Thymol 

 Blue permitted imrestricted development of all coliform organisms and inhibited 



