Micromethod for Biochemical Identification of Coagulase-negative Staphylococci

We have endeavored to elaborate a suitable method for easy and rapid identification in clinical microbiology laboratories of the different species of infection-inducing, coagulase-negative staphylococci. Ten type strains described by Kloos and Schleifer and 269 strains isolated from 95 patients were tested; the classical tests were used for determination of Staphylococcus species. Strains were identified by using the Kloos-Schleifer reference method and the micromethod simultaneously. After preliminary tests on 77 substrates, 19 were retained, 15 for determination of species and 4 to reveal biotypes. The substrates were placed in wells in a rigid strip of inert plastic. Inoculation of wells was carried out with rich microbial suspensions in a special medium; reading of substrate reactions was done after incubation for 48 h at 35 degree C. The intrasystem reproducibility was excellent, from 91 to 100% for the 19 substrates. It was in excellent agreement with the reference method, 100% for type strains and 97.9% for hospital-isolated strains. Because it is simple and easy to reproduce, the micromethod will be most useful in clinical and ecological microbiology laboratories.