Preparation of simulated clinical material for bacteriological examination

The preparation of mixtures of bacteria to mimic the flora found in pathological material is described. Such mixtures are useful for teaching, for practical examinations, for quality control of media and methods and for use in quality assessment schemes. The design of suitable mixtures is discussed and the stabilities of mixtures in transport media and in freeze-dried preparations are compared. Transport media provide short term storage for periods of several weeks and, with various modifications, are moderately successful with some, but not all, quite delicate pathogens. Freeze-drying however, provides greater stability over periods of months, allows preservation of delicate pathogens and is the preferred method where specimen quality is important.