DEHYDRATED CULTURE MEDIA 93 



BACTO 



MUELLER HINTON MEDIUM (B252) 



DEHYDRATED 



Beef, Infusion from 300 g. 



Bacto-Gasamino Acids, Technical . . 17.5 g. 



Starch 1.5 g. 



Bacto- Agar 1 7 g. 



Bacto-Mueller Hinton Medium duplicates the formula recommended by 

 Mueller and Hinton^ for the primary isolation of the gonococcus and menin- 

 gococcus. Sulfonamide resistance of gonococci and other microorganisms may 

 also be determined on this medium. 



In an attempt to develop a simple transparent medium containing no heat- 

 labile materials and capable of withstanding autoclaving, Mueller and Hinton 

 selected what they considered the most suitable complete medium available, and 

 attempted to break it into its essential components. The medium chosen for study 

 was the complex Gordon and Hine^ Pea Meal Extract Agar, which, in the 

 opinion of the senior author, had proved to be satisfactory for the primary iso- 

 lation of the meningococcus and the gonococcus. As a result of the fractionation 

 of the pea extract, it was found that the active portion was starch and not a 

 protein. Additional work showed that starch could replace the growth-promoting 

 properties of the pea extract and that the starch probably acts as a "protective 

 colloid" against toxic materials present in the medium. In addition, they found 

 that the tryptic digest of meat could be replaced by Bacto-Gasamino Acids, 

 Technical. Growth of the gonococcus and meningococcus on the developed 

 medium was highly satisfactory and colonies were usually large and easily recog- 

 nizable, especially with the aid of the oxidase reagent. 



Goodale et al.^ used the Mueller Hinton Medium to identify sulfonamide 

 resistant strains of the gonococcus. Nelson* used Bacto-Mueller Hinton Medium 

 in correlating sulfonamide resistance with the clinical picture in gonorrhoea. In 

 "Diagnostic Procedures and Reagents"^ of the American Public Health Associa- 

 tion, the Mueller and Hinton Medium is suggested for the isolation and trans- 

 portation of the meningococcus in the field or whenever blood is unobtainable. 



For the cultivation of the gonococcus, it is imperative to have the incubation 

 atmosphere saturated with moisture. Satisfactory conditions can be obained if 

 the plates of Mueller Hinton Medium are incubated in a closed container, which 

 contains cotton, a towel or a sponge saturated with water. A can with a suitable 

 cover, Novy jar, desiccator or any other convenient sized container capable of 

 retaining the moisture is entirely satisfactory. About 200 ml. of water added in 

 this manner is ample for a container of one or two gallons capacity. Plates incu- 

 bated under these conditions will give a luxuriant growth of many gonococci 

 when identically inoculated plates incubated in the ordinary manner in the in- 

 cubator show no growth. If the culture requires carbon dioxide for growth this 

 may be supplied as indicated under Bacto-Proteose No. 3 Agar, page 116. Car- 

 bon dioxide is recommended for isolation, but is not generally necessary, in the 

 presence of abundant moisture, for growth of isolated strains. 



To rehydrate the medium, suspend 38 grams of Bacto-Mueller Hinton 

 Medium in 1000 ml. of cold distilled water and heat to boiling to dissolve the 

 medium completely. Distribute in tubes or flasks and sterilize for 10 minutes at 

 10 pounds pressure (116°G.). The final reaction of the medium will be pH 7.4. 



It is recommended that the dissolved medium be distributed into test tubes 

 in 5 ml. quantities for slants or into 120-200 ml. flasks in 20 ml. quantities for 

 pouring plates. This medium must not be heated more than the sterilization 



