Abstract: Objective To improve the sensitivity of dermatophyte test medium (DTM) by optimizing its formula.Methods ①The effects of 4 key factors of DTM (nitrogen source,carbon source,pH value and indicator) were studied using orthogonal experiment and oneway grouped tests.②Ten-fold serial dilutions of Trychophyton rubrum suspension were placed on either DTM or reformed medium to determine the lowest limit of detection (sensitivity).③In order to evaluate the specificity of the assays,inoculation of a large number of fungus strains (18 species in 3 genus of dennatophyte and 14 species in 11 genus of mold) was also carried out in the above two types of medium.Results ①None of the modification of nitrogen source,carbon source,pH value and indicator in the medium had any significant effect (P>0.05) on the time of discoloration.The optimal formula,which was the most economical and convenient for recognition of discoloration,was 0.5% soy peptone and 0.5% glucose,with bromothymol blue as the indicator.②The sensitivity was 103 cfu/mL (10 cfu/medium) for both DTM and reformed medium.③All tested dermatophytes could alter the color of both media.Although most tested moulds could also result in a color change,their relative time of discoloration (the beginning time of discoloration minus that of growth) was≥1 day,whereas that of dennatophytes was≤0 day.Conclusions The reformed medium was more economical;it is also superior for early recognization of discoloration than DTM.

Key words: Arthrodermataceae, Culture media, Diagnosis