Dermatophyte Test Medium with Chloramphenicol & Cyclohexamide (Actidione)
This is a selective medium for the isolation of dermatophytes that includes a Phenol Red indicator to assist in the differentiation between dermatophytes and other pathogenic fungi. Although the low pH (5.5) of the medium inhibits most bacteria, Chloramphenicol is added to further reduce the risk when processing material that may be more heavily contaminated. Cyclohexamide (Actidione) is also added to suppress the growth of most yeasts and saprophytic fungi. Dermatophytes appear as fluffy white colonies and produce a red colour on the medium while other fungi cause the medium to become yellow due to acid production. Yeasts will also grow on this medium but are readily distinguished by their distinct white/creamy colonies and distinctive smell.
NB: Prolonged incubation should be avoided as this may cause fungi other than dermatophytes to turn the medium red