52 METHODS OF CULTIVATION OF BACTERIA 



Media for growing Trichophyta, Moulds, etc. 



1. Beer Wort Agar. Take beer wort as obtainable from the brewery, 

 and dilute it till it has an s.g. of 1100. Add 1'5 per cent, of powdered 

 agar, and heat in the Koch till it is dissolved (usually about two hours 

 are necessary). Filter rapidly and fill into tubes. Sterilise in the Koch 

 for twenty minutes on three successive days. If the medium is heated too 

 long it loses the capacity of solidifying. 



2. Sabouraud's Media. Sabouraud recommends the following 

 media : 



(1) Distilled water 1000 c.c. 



Maltose ("brute de Chanut") . . . 40 grms. 



Peptone ("granulee de Chassaing") . . 10 ,, 



Agar . . 18 ,, 



(2) Distilled water 1000 c.c. 



Glucose ("massee de Chanut") . . . 40 grms. 

 Peptone ("granule de Chassaing") . . 10 ,, 

 Agar . . . . . . ' . . 18 ,, 



In each case the ingredients are mixed and dissolved by gradually 

 raising to 120 C. in an autoclave. The medium is then rapidly filtered 

 through papier chardin (Cogit, 36 Boulevard Saint Michel, Paris) ; 

 when the filtrate begins only to pass in drops the fluid is transferred to 

 another filter, and this is repeated as often as is necessary. The medium 

 is distributed in wide test-tubes or Erlerimeyer's flasks, plugged with non- 

 absorbent cotton wool, and sterilised by slowly raising the temperature 

 to 120 C. 



To use these for isolating, say, the Tinea tonsurans, pick out an 

 infected hair, wash in absolute alcohol for a few seconds, then wash in 

 changes of sterile waterj; cut into small pieces and place these on the 

 surface of the medium ; incubate at 24 C. Usually, however, it is un- 

 necessary to disinfect .hair or skin scales from which dermophyta are to 

 be isolated. 



THE USE OF THE ORDINARY CULTURE MEDIA. 



The culture of bacteria is usually carried on in test-tubes 

 conveniently 6 x f in. These ought to be very thoroughly 

 washed and dripped, and their mouths plugged with plain 

 cotton wool. They are then sterilised for one hour at 170 C. 

 If the tubes be new, the glass, being usually packed in straw, 

 may be contaminated with the extremely resisting spores of 

 the b. subtilis. Cotton-wool plugs are universally used for 

 protecting the sterile contents of flasks and tubes from con- 

 tamination with the bacteria of the air. A medium thus 

 protected will remain sterile for years. Whenever a protecting 

 plug is removed for even a short time, the sterility of the 

 contents may be endangered. It is well to place the bouillon, 

 gelatin, and agar media in the test-tubes directly after filtration. 

 The media can then be sterilised in the test-tubes. 



