Two general types of culture media are essential to ensure the primary recovery of all clinically significant fungi from clinical specimens. One medium should be non-selective (such as Brain Heart Infusion Agar; i.e., one that will permit the growth of virtually all clinically relevant fungi) and other medium should be selective, specially tailored to isolate specific pathogenic fungi of interest.
For optimal recovery of fungal pathogen, a battery of media should be used, and the followings are recommended:
- Media with or without cyclohexamide (Cycloheximide is added to inhibit the growth of rapidly growing contaminating molds.)
- Media with or without an antibacterial agent (Chloramphenicol, Gentamicin and Ciprofloxacin are commonly used antibacterial for this purpose).
Antibacterial agents are used to kill the contaminating bacterial species. If the sample is taken from sterile site, it is not necessary to use media containing antibacterial agents.
- Brain-heart infusion (BHI) agar: It is a non-selective fungal culture medium that permits the growth of virtually all clinically relevant fungi. It is used for the primary recovery of saprophytic and dimorphic fungi
- Czapek’s agar: It is used for the subculture of Aspergillus species for their differential diagnosis.
- Inhibitory mold agar (IMA): Primary recovery of dimorphic pathogenic fungi. Saprophytic fungi and dermatophytes will not be recovered.
- It is generally Sabouraud’s dextrose agar with cycloheximide and chloramphenicol added.
- It is used for the primary recovery of dermatophytes.
- Niger Seed Agar: It is used for the identification of Cryptococcus neoformans.
- Potato Dextrose Agar (PDA): It is a relatively rich medium for growing a wide range of fungi.
- Sabouraud’s Heart Infusion (SABHI) agar: Primary recovery of saprophytic and dimorphic fungi, particularly fastidious strains.
Sabouraud’s dextrose agar (SDA):
- Sabouraud’s agar is sufficient for the recovery of dermatophytes from cutaneous samples and yeasts from vaginal cultures.
- Not recommended as a primary isolation medium because it is insufficiently rich to recover certain fastidious pathogenic species, particularly most of the dimorphic fungi.
- Sabouraud’s dextrose agar (2%) is most useful as a medium for the subculture of fungi recovered on enriched medium to enhance typical sporulation and provide the more characteristic colony morphology.
- Potato flake agar: Primary recovery of saprophytic and dimorphic fungi, particularly fastidious and slow growing strains.
- Koneman’s color atlas and textbook of diagnostic microbiology and
- Bailey and Scott’s Diagnostic Microbiology.