Agar plate tests of enhanced sensitivity for detecting biologically active products of staphylococcal filtrates.

Optimal conditions for detecting staphylokinase, phosphatase, protease, lipase, esterase, egg yolk factor, lysozyme, deoxyribonuclease, hyaluronidase, penicillinase, and alpha-, beta-, and delta-hemolysins in cell-free filtrates of selected strains of staphylococci by agar plate methods were established by studying the effect of factors such as buffer composition, pH, ionic strength, type of agar, nature and concentration of substrate, and certain metal ions. The final tests that evolved from this study are simple to perform, require only 6 mul of the sample per test, and are capable of detecting microgram and, in some cases, nanogram quantities of the product. The zones of reaction can also be quantitatively related to the amount of material present. The test may also be useful for the detection of extracellular products of other microorganisms.