Description
One of two media formulated by Kenner et al for use in detecting the presence of enterococci and other faecal streptococci in surface waters and foods by direct plating or by application of the membrane filter procedure for quantitative enumeration.1,2
In addition to sources of nitrogen,carbon, sulphur , vitamins and other growth factors supplied by proteose peptones and yeast extract, the medium contains maltose and lactose as fermentable carbohydrates together with sodium azide as a gram negative growth inhibitor. Two indicators, Tetraphenyltetrazolium Chloride (TTC) and Bromocresol Purple, are included, the first to detect the presence of rapidly metabolizing bacterial cells which reduce the TTC to form pink-red colonies, whilst the second changes the colour of the medium surrounding the colonies to yellow following acid production from fermented carbohydrates. TTC is incorporated in the Amyl dehydrated product as an alternative procedure suggested by the authors in which the medium (with TTC) is boiled rather than autoclaved, a procedure that may destroy TTC.
Sodium Glycerophosphate, provides buffering capacity and a source of high energy phosphate used in metabolic enzymic reactions. Sodium glycerophosphate in liquid form, Amyl Supplement SP 461, is supplied at no extra charge with the dehydrated product to be added separately due to it’s high level of hygroscopic activity and consequent effect on shelf life.
