TELLURITE-GLYCINE AGAR: A SELECTIVE PLATING MEDIUM FOR THE QUANTITATIVE DETECTION OF COAGULASE-POSITIVE STAPHYLOCOCCI

Abstract

A medium (tellurite-glycine agar) was developed that is superior to other media currently in use for the quantitative detection of coagulase-positive staphylococci. This medium contains 1.0% tryptone, 0.5% yeast extract, 0.5% mannitol, 0.5% K2HPO4, 0.5% lithium chloride, 1.0% glycine, 2.0% agar, and 0.02% potassium tellurite (added aseptically after sterilization). The pH is adjusted to 7.2 before autoclaving. A surface-plating technique is employed. Coagulase-positive staphylococci produce black colonies within 24 hours at 37[degree]C. Other microorganisms fail to produce visible growth within this time, with the exception of occasional coagulase-negative staphylococci that may grow. Most of these latter strains produce small gray colonies that are distinct from the type of colony produced by most positive strains. This medium was found satisfactory for the detection of coagulase-positive staphylococci in a variety of food products, fecal samples,soil, air, dust, and on the skin and mucous membranes.