How to test E. coli using the IDEXX Colilert 2000 method
What is it? E. coli (Escherichia coli ) is a fecal coliform bacteria that lives in the intestines of warm-blooded mammals, including humans. E.coli is a reliable indicator of fecal contamination in our water bodies, namely from sewage.
Why is it important? While E. Coli is naturally occurring, it can make us sick if we ingest it in our drinking waters or are exposed to it while swimming or engaging in other recreational water activities. Some areas have sewer overflow systems that have issues with human waste getting into the waterways, while other areas have problems with geese, ducks, and other animals, all of which can affect E. Coli levels.
What does it mean? Water quality can change quickly and frequently, so monitoring for E.coli and other fecal coliforms at the beach needs to be done frequently. Guidelines for monitoring E.coli at beaches, rivers, lakes, and swimming holes were developed based on epidemiological evidence. This science relates the concentrations of these fecal coliform bacteria to the incidence of swimming-associated gastrointestinal illness, such as diarrhea, observed among swimmers.
How to test
The IDEXX colilert test quantifies both total coliforms and E. coli in water samples, with results in 24 hours. When used in combination with a Quanti-tray system, counts of the bacteria can be recorded.
Sample collection:
- Wearing gloves, collect a water sample in a bottle or Whirl-pak bag.
- Place the sample in a cooler to prevent further bacterial growth
Lab processing:
- Add the colilert reagent to the water sample and mix thoroughly
- Pour the water sample/reagent mixture into the Quanti-Tray 2000.
- Seal the tray with the Quanti-Tray sealer
- Place the sealed tray in an incubator at 35°C ± 0.5°C incubator for 24 hours
- Note: dilution may be necessary
Read the results:
- Count Yellow wells = total coliforms
- Count Yellow/fluorescent wells = E. coli
- Report and share the data