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[Morphologic and physiologic characteristics of Costa Rica pathogenic fungi (Dermatiaceae)]
1Facultad de Microbiología, Universidad de Costa Rica.
Abstract:
Forty one strains of dematiaceous fungi from the Mycology collection of the University of Costa Rica were studied. Thirty three were pathogenic (Fonsecaea pedrosoi, Cladosporium carrionii, Xylohypha bantiana, Exophiala jeanselmei, Rhinocladiella aquaspersa, Phialophora verrucosa) and the other eight were contaminants (Hormodendrum sp.). Morphological studies were done using the slide culture technique. The physiological criteria used were: urease production, gelatin and Loeffler media liquefaction; xanthine, tyrosine, starch and casein hydrolysis; nitrate utilization; carbohydrate uptake; sensitivity to cycloheximide and thermotolerance in glucose-Sabouraud medium. The physiological tests did not provide characteristic patterns for the different genera of pathogenic fungi, even though these differences were detected in non pathogenic fungi; the tests may be useful for the quick separation of both groups. Physiological test may have a limited value in the identification of fungi and the morphological analysis cannot be substituted by physiological studies.
Insights
Morphological analysis is crucial for identifying dematiaceous fungi, as physiological tests showed limited value in distinguishing pathogenic species. These tests may aid in separating pathogenic from non-pathogenic fungi.
Area of Science:
- Mycology
- Medical Mycology
- Fungal Taxonomy
Context:
- Study of 41 dematiaceous fungi strains from the University of Costa Rica Mycology collection.
- Includes 33 pathogenic strains (e.g., Fonsecaea pedrosoi, Cladosporium carrionii) and 8 contaminants (Hormodendrum sp.).
- Utilized slide culture technique for morphological studies.
Purpose:
- To evaluate the utility of physiological tests in the identification and differentiation of pathogenic dematiaceous fungi.
- To compare the effectiveness of morphological versus physiological criteria in fungal identification.
Summary:
- Morphological studies were conducted using the slide culture technique.
- Physiological tests included urease production, media liquefaction, hydrolysis of various substrates, nitrate utilization, carbohydrate uptake, cycloheximide sensitivity, and thermotolerance.
- Physiological tests did not yield characteristic patterns for differentiating pathogenic fungal genera but could help separate pathogenic from non-pathogenic groups.
Impact:
- Highlights the limited value of physiological tests for specific fungal identification.
- Emphasizes that morphological analysis remains indispensable and cannot be replaced by physiological studies.
- Suggests physiological tests may be useful for preliminary separation of pathogenic and non-pathogenic fungal isolates.