176 DIFGO MANUAL 



the development of Gram-negative spore formers as well as Gram-positive 

 microorganisms. Escherichia produce yellow colonies surrounded by yellow 

 zones; Aerobacter produce large mucoid colonies, usually surrounded by yellow 

 zones; paracoli and other lactose non-fermenting organisms produce colonies 

 usually surrounded by blue zones, on this medium. Proteus and other organisms 

 have little tendency to form spreading colonies. Counts of coliform organisms 

 on Tergitol 7 Agar were found to be 30 per cent higher than on other selective 

 media for members of this group. Tergitol 7 Agar is inoculated by smearing 

 the surface wdth the specimen using a bent glass rod. As much as 0.1 ml. of 

 inoculum may be used per plate if the surface of the medium is dry. Pour plates 

 do not give satisfactory results. 



The addition of 40 mg. of TTC to a liter of sterile Tergitol 7 Agar permitting 

 the confirmation of E. coli after 10 hours incubation was described by Chapman. ^ 

 E. coli does not reduce the dye while other coliform organisms rarely fail to do 

 so. Surface colonies of E. Coli on this medium are greenish yellow surrounded 

 by a yellow halo while other coliform surface colonies are dark red. Readings can 

 be made following incubation at 37°C. for 10 hours. Chapman^ also reported 

 that Tergitol 7 Agar with added TTC (40 mg. per liter) gave a selective 

 medium for the isolation of Monilia and other fungi. Monilia growing on this 

 medium produce white circular convex entire colonies about 1 mm. in diameter 

 in 24-48 hours. The colonies may appear pale blue because of the color of the 

 medium. Yeasts produce red colonies. Since the medium permits the develop- 

 ment of coliform organisms this fact must be taken into consideration in the 

 isolation of Monilia from specimens. Chapman* also used Tergitol 7 in a modi- 

 fied Sabouraud Maltose Agar, for the isolation and differentiation of Monilia 

 and other fungi. This medium is described in detail on page 239, under Bacto- 

 Sabouraud Maltose Agar. 



To rehydrate the medium, suspend 33 grams of Bacto-Tergitol 7 Agar in 

 1000 ml. of cold distilled water. Heat to boiling to dissolve the medium com- 

 pletely. Distribute in tubes or flasks and sterilize in the autoclave for 15 minutes 

 at 15 lbs. pressure (121°C.). Final reaction of the medium will be pH 6.9. 



1 J. Bact., 53:504:1947. * Trans. New York Acad. Sci. Series II, 



BAm. J. Pub. Health, 41:1381:1951. 14:254:1952. 



8 In press. 



BACTO 



MOTILITY SULFIDE MEDIUM (B450) 



DEHYDRATED 



Bacto-Beef Extract 3 g. 



Proteose Peptone No. 3, Difco .... 10 g. 



/-Cystine, Difco 0.2 g. 



Ferrous Ammonium Citrate 0.2 g. 



Sodium Citrate 2 g. 



Sodium Chloride 5 g. 



Bacto-Gelatin 80 g. 



Bacto-Agar 4 g. 



Bacto-Motility Sulfide Medium is a semisolid medium suitable for determining 

 motility and the production of hydrogen sulfide from /-cystine. It is prepared 

 according to the formula given by Hajna,^ and used in the rapid method of 

 differentiation and identification of bacteria of the intestinal group as described 

 by him. 2 As pointed out by Hajna,^ this medium is the semisolid agar-gelatin 

 medium of Edwards and Bruner^ modified to permit observation of motility 

 and simultaneous hydrogen sulfide production from /-cystine. Hydrogen sulfide 



