A note upon the maintenance of cultures of Bacterium typhosum for testing by the Rideal-Walker method

Extract

The British Standard Technique for Determining the Rideal-Walker Coefficient of Disinfectants (no. 541—1934), in laying down the procedure to be adopted with regard to the test typhoid bacillus culture, recommends that a fresh culture be obtained each month from the National Collection of Type Cultures. In all probability this is the best procedure; it does, however, sometimes happen that a test is required urgently when a fresh culture is not available. The following notes upon our own experience in maintaining cultures may therefore be of some interest. It is our practice to obtain fresh cultures whenever we are called upon to carry out other than routine tests unless a recent one has been obtained, and many of these cultures have now been running for a number of years. On the arrival of the culture from the N.C.T.C. it is subcultured on to an agar slope and “incubated” at room temperature in a dark cupboard. 2% agar is used in a broth prepared by the tryptic digestion of ox heart. Further subcultures are made at intervals of one month. It is our usual practice to start a series of broth cultures from such slopes not less than 14 days after sowing.