Membrane filtration

The membrane filtration method is a common lab test used to detect enterococci in a water sample. First, a measured amount of water is poured through a special filter that traps bacteria. The filter is then placed on a nutrient-rich agar plate designed to help enterococci grow. The plate is incubated at a set temperature for about 24–48 hours. If enterococci are present, they form visible coloured colonies on the filter. By counting these colonies, scientists can estimate how many enterococci were in the original sample, reported as colony-forming units (CFU) per 100 millilitres of water.