[Escherichia coli, other Enterobacteriaceae and additional indicators as markers of microbiologic quality of food: advantages and limitations].

The 93/43 European Union directive assigns to the food and catering industries the main responsibility for an integrated safety and quality assurance strategy in the food chain. Relying on hazard analysis, followed by design and adoption of control of all critical points and practices ("HACCP"). Hiatus-free compliance with such HACCP-based Codes of Good Practices is to be assessed by monitoring, recording results on process performance charts and gauging such data against experimentally established, attainable and maintainable references ranges ("standards"). Marker microorganisms are a major analytical tool for validating compliance in the sense of the EU directive. They should be expertly chosen amongst microbes usually present in food so that their, whose presence in quantities exceeding predetermined levels point to a lack of microbiological integrity of a food product. This may encompass (i) the potential presence of taxonomically, physiologically and ecologically related pathogens, markers are called index organisms; or else (ii) a lack of process integrity; in this case, markers are termed indicator organisms. The classical index organism was E. coli, introduced in the 1980's to monitor drinking water supplies. It is still used as an appropriate marker to assess the bacteriological safety of raw foods. In the 1920's the coli-aerogenes ("coliform") group was adopted as an indicator to validate the adequate processing, i.e. pasteurization of dairy products. Since the 1950's the entire Enterobacteriaceae taxon is preferred for the latter purpose because it is better defined in determinative sense and includes more organisms of significance. In some food and water supplies, processed for safety, more vigorous or more resistant organisms than the Gram-negative rods are reliable supplementary markers. These include Enterococcus spp., spores of the Clostridium genus, and bacteriophages of E. coli and Bacteroides fragilis mimicking the fate of enteric viruses under particular ecological conditions. Population surveys conducted by the authors provided ranges for epsilon-factors. Those factors were defined as the proportion between colony forming units (cfu) numbers of index organisms and the pathogenic agent to whose potential occurrence they are expected to point. Epsilon factor values obtained for thermotropic Enterobacteriaceae in relation to Salmonella spp. allow the calculation of the probability that the pathogen has been reliably eliminated by the processing of initially contaminated raw materials, when cfu's of the marker organisms remain below a reference range previously fixed.