Nagler plate

This is a test done to determine if Clostridium perfringens produces lecithinase, a toxin.
The agar plate is egg based which provides the lecithin. Its colour is similar to a nutrient agar plate. These plates dont have a long shelf life so are either made up in small quantities of made when required. the plates need to be sealed in plastic bags and refridgerated prior to use. Allow plates to reach room temperature before use.
divide the plate in half using a permanent marker. Name one half as the seeded portion. Seed that half with the lecithinase.
Streak your test organism, positive and negative controls perpendicular to the dividing line, parallel to each other, using a line streak. Ensure that you start streaking from the unseeded half to the seeded half. This is so that no lecithinase is carried over to the unseeded half.
Incubate the plates anaerobically for 18-24 hours at 37 degrees.
When lecithin combines with lecithinase, it produces opalescence, which has a cloudy, milky, opal looking effect. Therefore a positive reaction would be opalescence on the unseeded half, and no opalescence on the seeded half. Very pretty!!in the seeded half, the lecinthinase is neutralised by the antitoxin, thats why no opalescence is seen.
Ensure that before reading your test you read the positive and negative controls.