Roth R-Card (E. coli and total coliforms)
What is it? E. coli (Escherichia coli) is a bacteria and is in the fecal coliform subgroup. It lives in the intestines of warm-blooded mammals, including humans. While E.coli is healthy and 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. E. coli plays a central role in measuring the health risks associated with sewage and contamination for natural water bodies, such as lakes, rivers, swimming holes, and marine beaches. Total coliforms and other coliforms are also used as indicators of fecal contamination.
Why is it important? E.coli is naturally occurring in our environment. E.coli is a reliable indicator of fecal contamination in our water bodies, namely from sewage. In other words, we can measure E.coli in water to understand if wastewater and stormwater have polluted a water body. E.coli is primarily used to monitor levels of fecal contamination in freshwater.
How to test
Sampling
- Rinse the sample cup 3 times
- Collect the sample 15cm below the surface, or as deep as possible without including sediment.
- Fill the syringe to the 1mL mark (tap out any air bubbles!).
- Gently lift the film and squirt water onto the card.
- Roll the film down onto the sample, allowing the water to spread into a circular pattern between the film and the card. The water should be within the area of the top film but doesn’t need to cover the entire area. DO NOT press the film down… allow it to spread.
- Repeat for each of the three cards for one location using the same sample.
- Allow the R-Cards to seal (1-2 minutes) then place into the bag and seal.
Processing
- Keep the cards out of direct sunlight and keep cool. Use a cool pack if it’s warm weather but DON’T put the cards on ice.
- Switch on the Incubator and allow it 20 minutes to warm up to 35 °C .
- Cards should be placed in the incubator within 3 hours of collection.
- Incubate the cards for 24 hours before counting the colonies.
- Average the result for the three cards, then multiply by 100 to report Colony Forming Units (CFU) per 100mL.
Incubate your R-Card
- As part of the R-Card test kit, we provide a ‘home incubator’ which is a small USB-C powered unit originally designed for home incubation of small eggs. This allows a controlled and consistent incubation temperature.
- Set the incubator temperature to 35deg C (it defaults to 37.8 deg), and allow it to warm up to that temperature before putting in the R-Cards.
- Count results at 24 hrs. after placing the cards in the incubator.
- Do not count any colonies that may develop after 48 hrs. as the E. coli and coliforms that you are monitoring are very fast growing and will definitely be visible within that time period.