A new test of disk-diffusion to help in staphylococci identification.

A modified carbohydrate fermentation test (MCFT) of disk-diffusion assay was performed using a peptone-free agar medium, in order to improve the identification of clinical staphylococci species. Results were compared with the standard method of carbohydrate fermentation in tubes (SCFT) containing methyl red broth. MCFT was able to identify correctly 12 different species of staphylococci from the ATCC collection and 646 clinical isolates. MCFT showed sensitivity between 91.6% and 100% and specificity between 99.6% and 100%, for the different carbohydrates studied. MCFT could replace the SCFT, with the evident advantage of reducing time for materials preparation. The method presented herein is easy to perform in clinical or research microbiology laboratories, because it can differentiate species of staphylococci.