Heterotrophic plate count
Z TSENZ
- Slovak term: Slovenský termín
- A test used to estimate the total number of all types of bacteria in an environmental sample, usually water (WHO 2003).
Explanation
The lower the HPC, the better the biological water quality. Other names for the procedure (within the water industry) include total plate count, standard plate count, plate count and aerobic plate count.
Although standardized methods have been formalized, HPC test methods involve a wide variety of test conditions that lead to a wide range of quantitative and qualitative results. Temperatures employed range from around 20°C to 40°C, incubation times from a few hours to seven days or a few weeks, and nutrient conditions from low to high. The test itself does not specify the organisms that are detected (WHO 2003).
Example
HPC measurements are used:
- to indicate the effectiveness of water treatment processes, thus as an indirect indication of pathogen removal;
- as a measure of numbers of regrowth organisms that may or may not have sanitary significance; and
- as a measure of possible interference with coliform measurements in lactose-based culture methods. This application is of declining value, as lactose-based culture media are being replaced by alternative methods that are lactose-free (WHO 2003).
