Description
Amyl Lactose Egg Yolk Agar, AM 721, containing neutral red indicator is used to differentiate strains of Clostridia according to their ability to produce the enzymes lecithinase and/or lipase, and whether or not they are able to ferment the carbohydrate lactose. The medium was developed by Willis and Hobbs1 and is specified by Standards Australia for use in the examination of food for the presence of Clostridium perfringens2, colonies of which produce a marked zone of opalescence extending beyond the colony with an acid (pink) reaction which is initially peripheral but, on oxidation, produces a pink colour within the colony due to fermentation of lactose. Lipase producing Clostridia such as Cl.sporogenes and Cl. botulinum produce an opalescence restricted to the medium underlying the colony and an overlying iridescent “pearly-layer” as the enzyme hydrolyses free fats into fatty acids and glycerol.
