Enterococci
What is enterococci?
Enterococci is a fecal coliform bacteria, similar to E.coli. It lives in the intestines of warm blooded mammals, including humans. While enterococci 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. Enterococci also plays an important role in helping us to measure the health risks associated in swimming in natural water bodies, such as lakes, rivers, swimming holes, and marine beaches. It is mainly used in marine water, but is increasingly used in freshwater as an indicator of health risk to bathers.
Why is enterococci important in recreational water monitoring?
Enterococci is naturally occurring in our environment. This faecal coliform is an indicator of faecal contamination, namely from sewage, in our water bodies. Enterococci is primarily used to monitor levels of faecal contamination in marine (salty) water, but increasingly it is being used in freshwater to assess health risks.
Guideline values for enterococci have been developed based on the analysis of epidemiological evidence relating concentrations of these organisms to the incidence of swimming-associated gastrointestinal illness observed among swimmers.
How does the quantity of enterococci in water samples measure health risks?
The concentration of enterococci in a water sample is typically measured per 100ml. Methods to measure enterococci include membrane filtration (CFU), multi tube fermentation (MPN), and more rapid processing methods like qPCR methods.
In Canada, the federal government guidelines, Guidelines for Canadian Recreational Water Quality, for enterococci are the following
Enterococci (Primary-Contact Recreation)∗
Geometric mean concentration (minimum 5 samples) ≤ 35 enterococci /100 mL
Single sample maximum concentration ≤ 70 enterococci /100 mL
In the USA, the Environmental Protection Agency’s (EPA) Recreational Water Criteria are the following:
RECOMMENDATION 1: MAGNITUDE
Culturable enterococci at a geometric mean (GM) of 35 colony forming units (CFU per 100 milliliters (mL) and a statistical threshold value (STV) of 130 cfu per 100 mL, measured using EPA Method 1600, or any other equivalent method that measures culturable enterococci.
RECOMMENDATION 2: MAGNITUDE
Culturable enterococci at a GM of 30 cfu per 100 mL and an STV of 110 cfu per 100 mL, measured using EPA Method 1600, or any other equivalent method that measures culturable enterococci.
Enterococci Sample Collection and Processing Protocol
There are many sample collection and processing methods available for quantifying enterococci concentration in water. However, to date, most require a laboratory for processing results.
The most common methods for measuring the concentration of enteroccocci water bodies are :
Membrane filtration
Multi Tube fermentation, such as IDEXX Laboratories colilert methods.
Quantitative Polymerase Chain Reaction (qPCR)
These are known as “persistent” methods, and they enumerate the number of enterococci in the samples. Results from these methods are available between 4 to 48 hours.
Models for predicting the concentration of enterococci at beaches and other recreational water sites are also used. These models work just like weather forecasting does. Using historical water quality data, current and historical weather data, and other parameters such as geography and currents, the water quality can be forecasted. Predictive models are able to offer information to beachgoers about what is happening right now, and can even forecast up to two days ahead.
How to test your water body for Enterococci
Monitoring enterococci in the water is not a field test. If you are interested in monitoring enterococci you will need to collect water and process the sample at a lab. You’ll need your own in-house lab to process sample results, or you can consider bringing your samples to a local environmental lab.
Public Health Ontario provides a helpful sample collection, handling, and processing guide.