Modified oxidase and benzidine tests for separation of staphylococci from micrococci

Abstract

Two simple and rapid methods for the separation of staphylococci from micrococci are described. They are based on modified oxidase and benzidine tests. Micrococci and Staphylococcus sciuri yield a blue color with a 6% solution of tetramethylphenylenediamine in dimethyl sulfoxide, whereas all of the other staphylococci exhibit no coloration. Best's results were obtained with overnight cultures on blood agar. The presence of c-type cytochromes i micrococci and S. sciuri could be detected with benzidine; all noncovalently linked heme groups are removed before the addition of the benzidine reagent. The oxidase test is the simplest and most rapid method for the separation of staphylococci (except S. sciuri) from micrococci, if the nutritional requirements and the time of incubation are strictly followed. This test is especially recommended for the examination of clinical material in which S. sciuri is usually not found.