Test Preparation

• 1). Obtain a testing kit. Laboratories have developed simple, at-home test kits designed to produce quick, accurate results by laymen. These can be now be easily obtained online. Read the instructions before proceeding.
  
  
• 2). Sterilize a glass jar. Cover it completely with water and boil uncovered for 15 minutes. Allow the jar to cool thoroughly.
  
  
• 3). Collect the water to be tested and bring it back to the test site. Place the sample on ice, if it will be kept for more than an hour before beginning the test.
  
  
• 4). Determine the amount of sample required, as indicated in the directions. Amounts will vary depending upon the source. Environmental sources such as pond water typically require a larger sample than well or municipal sources.
  
  
• 5). Label each petri dish with a wax pencil or sharpie. Indicate the source of the sample, date taken and indicator/dye being used.
  
  

Transfer the Sample

• 1). Transfer the recommended sample amount, as determined above, into the testing bottle contained in the kit. To maintain sterility, do not touch the mouth of the testing bottle or rim of sample container. Swirl the testing bottle to mix the sample with the indicators and growth medium contained in it.
  
  
• 2). Transfer the sample into the labeled petri dishes. Lift the lid partially at approximately a 45 degree angle. This will minimize bacteria from the air. Quickly pour the sample into it.
  
  
• 3). Drop the lid onto the petri dish and gently swirl, until the entire dish is covered with liquid. Do not splash the sample.
  
  

Incubation and Inspection

• 1). Place the dish right-side up in a warm, level spot while it is still liquid. This can be any room temperature location free of drafts. However, E. coli will grow more quicker under warmer conditions. A spot near a light source will generate additional heat. The dish will solidify in approximately 45 minutes and should be left undisturbed to grow for 48 hours.
  
  Dishes can be placed in an incubator at 35 degree Celsius for 24 hours, should you have access to one.
  
  
• 2). Count the number of purple colonies that appear on the dish disregarding any light blue, blue-green or white colonies. Purple is an indication of the presence of E. coli. Record the number of colonies.
  
  
• 3). Divide 100 by the number of milliliters (ml) you used for your sample. Multiply the number by the number of E. coli found on your plate. This is termed the Standard Plate Count (SPC) method, which is used in most microbiology laboratories. Record this number.
  
  

Disposal and Reporting

• 1). Dispose of the petri dish in a safe manner. E. coli is considered a bio-hazard and contact with it could result in illness. The dish can be placed in a pressure cooker and cooked at 15 pounds for 15 minutes. This is considered the most effective disposal method, because it mimics the effects of a medical autoclave.
  
  
• 2). Place the dish in a sealed oven-proof bag and heat in a 300 degree oven for 45 minutes, if no pressure cooker is available. The dish and sample bottle can also be placed in a large pan covered with water and boiled for 45 minutes.
  
  
• 3). Place five milliliters (ml) of straight bleach onto the surface of the medium of the plate, if the above methods cannot be used. Allow it to sit for at least five minutes.
  
  
• 4). Place sterilized container(s) in a water-tight bag and discard in the trash.
  
  
• 5). Contact your local health department if your test confirms the presence of E. coli. If your sample was from a source that supplies your home with drinking water, do not drink it or ingest it from any sources such as a shower. Follow the guidelines given to you by the health department to keep your family safe and remove the source of contamination.