Coliform bacteria are commonly found in the gastrointestinal tract of warm-blooded animals, such as humans and other mammals. When these animals excrete waste, a significant number of coliforms are released in their feces. Elevated levels of coliforms in a water sample often indicate contamination by animal or human excrement. 

While the majority of coliform bacteria are benign, certain strains, notably some variations of the Escherichia coli (E. coli) bacterium, can pose health risks. Additionally, numerous pathogenic bacteria and parasites, responsible for diseases such as typhoid fever, hepatitis, gastroenteritis, and dysentery, can be transmitted through fecal matter. Thus, the presence of coliforms suggests the potential presence of harmful pathogens. Monitoring coliform levels in drinking water and recreational (rivers, streams and lake) waters is crucial for safeguarding public health.

To ascertain the presence and concentration of coliform bacteria, bacterial enumeration techniques are employed. This involves inoculating a sample of the water onto a specialized agar (MacConkey Agar) medium that provides nutrients conducive to coliform growth. After an incubation period, bacterial colonies develop on the agar plate. By identifying and quantifying these colonies, we can determine the concentration of coliforms in the water sample. This methodology aids in extrapolating the presence of other bacteria and parasites in the water.

Water samples were taken from each of the sample sites by inverting sterile sample bottles below the water line. The cap was removed and the bottle was oriented upright to fill completely. 0.5 mL samples were transferred from the sample bottles to MacConkey Agar. The ager was cultured in a 75F incubator for 48 hours. The total number of colony forming units (CFU) were counted and multiplied by 200 to determine the number of CFU's per 100 mL's of water.  

According to the Michigan Department of Energy and Great Lakes (EGLE), "County health departments need to take a minimum of three samples each time a beach area is monitored. The daily geometric mean calculated from these samples must be below 300 E. coli per 100 milliliters for the water to be considered safe for swimming. Sometimes one or two of the samples may be above 300, but if the daily geometric mean is below 300, the beach is not in violation of the water quality standard. The county health departments frequently sample more than once a month. A minimum of five sampling events (consisting of at least three samples per event) must be collected within a 30-day period for the results to be considered a reliable indication of water quality. After 30 days, a geometric mean is calculated for all the individual samples collected within that time frame. This 30-day geometric mean must be below 130 E. coli per 100 ml for the water to be considered safe for swimming. " Additional information from EGLE can be found on the following website. 

In the United States, the Environmental Protection Agency (EPA) sets standards for coliform levels in water as well. Total coliform bacteria should not exceed 5 colony-forming units (CFU) per 100 milliliters (mL) of water for drinking water, and fecal coliform or Escherichia coli (E. coli) should not be detected in any 100 mL sample of drinking water. The EPA's guidelines for recreational water quality primarily focus on E. coli levels. The EPA recommends that E. coli levels not exceed 126 colony-forming units (CFU) per 100 milliliters (mL) of water for primary contact recreation, such as swimming.

Our cultures are a "snapshot in time." We did not perform a positive or negative control. Nor did we run any replicates. For the sake of time when testing we only took a single sample from each test site. Additional testing should be performed to confirm the number of CFU's at the various Ionia County waterways.