Morphologic and physiologic studies of three dematiaceous pathogens.

Area of Science:

• Medical Mycology
• Fungal Taxonomy
• Clinical Microbiology

Background:

• Uncertainty in identifying dematiaceous molds from human bronchial washings.
• Need to clarify the relationship between Dactylaria gallopava, Scolecobasidium constrictum, and Ochroconis constricta.

Purpose of the Study:

• To investigate the morphologic and physiologic characteristics of specific dark molds.
• To resolve taxonomic ambiguities and propose a new fungal combination.
• To assess the clinical significance of these fungi.

Main Methods:

• Morphologic examination of fungal isolates and type specimens.
• Physiologic testing, including growth at different temperatures and biochemical reactions (gelatin hydrolysis).
• Comparative analysis of anamorphic structures and conidiophore development.

Main Results:

• All tested isolates exhibited similar morphologic features, primarily two-celled, cylindrical blastoconidia.
• Sympodial conidiophore development was not a reliable distinguishing feature.
• Two distinct physiologic subgroups of Dactylaria constricta were identified based on growth at 37/45°C, gelatinase activity, and Mycosel agar growth.

Conclusions:

• A new combination, Dactylaria constricta, is proposed for Scolecobasidium constrictum based on morphologic similarity.
• Physiologic differences differentiate D. constricta into two subgroups.
• Dactylaria constricta should be considered a potential pathogen in clinical specimens.