DEMONSTRATION OF STAPHYLOCOCCAL CLUMPING FACTOR AND FREE COAGULASE IN SOFT AGAR MEDIA

Abstract

All strains of staphylococci tested produced diffuse colonies in trypticase soy-0.15% agar. Addition of human or rabbit plasma or of bovine fibrinogen to the basal medium induced colonial compactness only in clumping factor positive strains. On addition, to the basal medium, of both 1.0% plasma and 0.4% fibrinogen, or of sufficient plasma alone, coagulation zones appeared around colonies of free coagulase producers. Incorporation of 0.3% bovine albumin intensified the coagulation zone. This method not only demonstrated clumping factor and coagulase activity simultaneously, but also revealed rare strains which were positive for one of these properties exclusively and strains which were mixed populations. Detection and isolation of variants were thus facilitated.