SELECTIVE CULTURE OF SPOILAGE AND INDICATOR ORGANISMS1,2

Abstract

Methodology for detection and enumeration of microorganisms has involved an increasing awareness of the role of cellular injury on analytical microbiology. Injury has been shown to result from heat, freezing, chemicals, irradiation, and similar treatments. All of these treatments are commonly used in the processing and preservation of foods. Since injured microorganisms can recover and cause food spoilage or since injured pathogens can recover and become infective, the detection of injured pathogens or of injured index microorganisms is imperative in order to assure the safety of foods. The detection of injured microorganisms becomes more difficult with the use of selective media. Environmental conditions or added inhibitors which are used to allow only the development of the types being sought may exert unsuspected inhibition. This shortcoming in our methodology appears to occur in the use of selective media in quantitative determinations, as well as in enrichment media that are designed to promote the growth and easier qualitative detection of a specific pathogen or indicator organism. One of the most pressing problems facing the food microbiologist at this time appears to be means to resuscitate an injured microorganism so that it can be detected selectively in the quantitative or qualitative examination of foods.