24 CULTURE MEDIA 



SUGAR BOUILLON 



The sugar media ordinarily used for determining fermentation or gas production 

 are those of glucose and lactose. In special work such carbohydrates as saccharose 

 and maltose are used. The alcohol mannite is used in differentiating strains of 

 dysentery bacilli. 



To make, simply dissolve i or 2 % of the sugar in sugar-free bouillon or that made 

 from meat extract. Tube in Durham's or the ordinary fermentation tubes and 

 sterilize in the autoclave at only about 5 pounds' pressure for fifteen minutes, or in 

 the Arnold. Ordinary peptone solution is a good substitute for sugar-free bouillon. 



Too high a degree of heat may turn the sugar bouillon brownish. The nature 

 of the sugar itself may further be affected by too high a temperature. Many of 

 the carbohydrates added to bouillon are liable to be split up on subjection to any 

 marked sterilization. Maltose is particularly unstable. It is best to make about 

 20% solution of the carbohydrates in distilled water and sterilize in small flasks adding 

 enough to the sterile bouillon to give a i % solution. Inulin usually contains resist- 

 ant spores so that its sterilization may need the autoclave. One of the great diffi- 

 culties about reporting on sugar reactions is the possibility of not working with a 

 chemically pure sugar as well as with one changed by too much heat. Inulin is a 

 polysacchoride resembling starch but does not give the iodine reaction. It is 

 obtained from the roots of chicory or dandelion. For further notes on carbohydrates 

 see water analysis. 



BESREDKA'S EGG BOUILLON 



ioo c.c. broth without salt; 80 c.c. 10% egg-white solution; 20 c.c. 10% yolk of 

 egg solution. 



The egg-white solution is prepared by constant heating while adding distilled 

 water little by little. It is then filtered through absorbent cotton and heated to 

 iooC. Then filter through filter-paper. 



This opalescent liquid is then put into tubes or flasks and sterilized at nsC. for 

 twenty minutes. 



To ioo c.c. of -10% emulsion of egg yolk in water you add about i c.c. of N/i 

 NaOH solution. One should add enough of this caustic soda solution to clarify the 

 emulsion slightly; it should still be opaque when in a rather thick layer. Heat to 

 iooC., then filter and finally sterilize at ii5C. for twenty minutes. 



The bouillon is a 50 to 75% meat infusion with peptone. 



This is an excellent medium for growing pneumococci, streptococci, meningococci 

 and gonococci; even the organism of pertussis will grow on this medium. Of course 

 such organisms as the typhoid-colon group, cholera, diphtheria and pathogenic 

 anaerobes grow readily on it. 



The medium is particularly recommended for growing tubercle bacilli. For this 

 purpose the peptone in the bouillon is omitted as it is found that tubercle bacilli 

 grow better without it. Besredka found that tubercle bacilli grew better when he 

 omitted the addition of glycerine to his medium. 



It will be noted that for tubercle bacilli the medium should contain neither pep- 

 tone, salt nor glycerine. 



In the course of two to three weeks we have a thick membranous growth. 



