The selection and preparation of some media in common use in one bacteriology laboratory

Abstract

There are philosophical as well as cogent practical reasons why larger laboratories should select and prepare most of their own media rather than attempt to purchase them ready for use. At The Prince of Wales Hospital laboratory. the most commonly used agar media arc, nutrient horse blood, MacConkey and a medium for determining the antibiotic sensitivity of isolates. In 1978 the number of plates of these media alone which were prepared amounted to almost 150 000. These plates were prepared by reconstituting dehydrated media which were obtained commercially. A brief description will be given of the organization of the media department which is capable of pouring from 2500 to 4000 plates in a period of one hour. The selection of any particular medium is based on a number of considerations, including availability of particular brands of dehydrated media, the reproducibility of the amount and type of bacterial growth obtained. and the nature of the bacteria to be isolated. These will be discussed together with a description of methods used for the evaluation of the performance of different media.