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Medium for susceptibility testing and yeast phase conversion of Blastomyces dermatitidis
Mycopathologia
|July 1, 1986
Summary
Both cottonseed and TAC media efficiently convert Blastomyces dermatitidis mycelia to yeast phase. Yeast phase is generally more susceptible to antifungals like Amphotericin B and ketoconazole, necessitating phase-specific susceptibility testing.
Area of Science:
- Medical Mycology
- Antimicrobial Susceptibility Testing
Background:
- Blastomyces dermatitidis exists in both mycelial and yeast phases.
- The yeast phase is the parasitic form responsible for infection.
- Antifungal susceptibility testing is crucial for effective treatment.
Purpose of the Study:
- To compare cottonseed protein agar and modified Tween-albumin casein hydrolysate (TAC) medium for yeast phase conversion of Blastomyces dermatitidis.
- To evaluate the antifungal susceptibility of both yeast and mycelial phases of Blastomyces dermatitidis.
Main Methods:
- Comparative study of two culture media (cottonseed agar and TAC medium) for Blastomyces dermatitidis yeast phase conversion.
- Antifungal susceptibility testing of yeast and mycelial phases against Amphotericin B and ketoconazole.
Main Results:
- Both media achieved >95% conversion of B. dermatitidis from mycelial to yeast phase within three days.
- TAC medium offers clearer visualization of yeast growth compared to opaque cottonseed agar.
- Yeast phase strains generally exhibited higher sensitivity to Amphotericin B and ketoconazole than mycelial phase strains.
Conclusions:
- Both cottonseed agar and TAC medium are effective for yeast phase conversion of Blastomyces dermatitidis.
- Antifungal susceptibility testing should be performed on the pathogenic yeast phase for optimal therapeutic guidance.
- Differences in susceptibility between phases and media highlight the importance of tailored testing.