Sanitary Indicator Microorganisms and Their Characteristics

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Microbes are ubiquitous in nature. Any type of ecosystem comprises a vast number of inherent microbial residents maintaining its integrity.

Every natural or artificial biotope temporarily or constantly contains microbes able to cause human diseases. Nevertheless, it is rather difficult to determine all of pathogenic agents in the environmental samples. The number of pathogenic species is enough high and their properties are extremely variable. Therefore, the methods for their identification and continious monitoring are highly diverse, someway laborious, time-consuming and thereby expensive. A new methods of massive parallel genetic identification of microorganisms are extensively designed now (e.g., DNA microarray technologies), but they still remain more the subject of research interests.

Instead of pathogenic bacteria so-called sanitary indicator microorganisms are tested and monitored. The elevation of the quantity of indicator microorganisms corresponds to the increased probability of pathogenic bacteria presence in the environment.

Sanitary indicator microorganisms possess several common traits:

  1. a) they are constant inhabitants of human or animal body that is followed by their continuous discharge to the environment in considerable amounts;
  2. b) they have to survive in the environment in terms comparable with pathogenic bacteria or longer;
  3. c) lack of reproduction in the environment;
  4. d) absence of propagation in another biological reservoir or host except human or animal body;
  5. e) they should be assessed easily by appropriate and reliable laboratory methods of microbiological monitoring.

Any environmental medium is characterized by its particular indicator microorganisms.

Besides, the sanitary quality of a certain environmental medium is assessed also by its overall microbial contents.

This sanitary quality index is known as total plate count (total viable count, or total microbial count) that is equal to the total number of microbial cells (colony forming units or CFU) present in 1 g or in 1 ml of the sample.