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Phialophora parasitica, an emerging pathogen
Abstract:
Monoconidial cultures derived from 12 clinical and environmental isolates of Phialophora parasitica were compared with respect to morphologic and physiologic characteristics and response to antifungal agents. No yeast cells were seen in 1- and 3-week-old slide culture preparations. Also, not all of the distinguishing characteristics of this species were displayed by all isolates on all media examined. Although the isolates grew on Sabouraud agar with chloramphenicol and cycloheximide, some inhibition was observed. All cultures were strongly urease-positive and hydrolyzed casein and starch; most decomposed tyrosine but not gelatin. All but one environmental isolate grew well at both 23 and 37 degrees C, but none grew at 40 degrees C. In the sensitivity testing the isolates did not vary much in their response to each drug, although some anomalies were observed. Amphotericin B and miconazole had minimum inhibitory concentrations in the low sensitivity range (2.0-8.0 and 2.5-10 micrograms m-1 respectively), for most isolates, and most isolates were resistant to both 5-fluorocytosine and ketoconazole. Limited observations were made on three other Phialophora species which might be confused with P. parasitica.
Insights
This study characterized Phialophora parasitica isolates, finding variations in traits and antifungal responses. Most isolates were sensitive to amphotericin B and miconazole but resistant to 5-fluorocytosine and ketoconazole.
Area of Science:
- Medical Mycology
- Clinical Microbiology
Background:
- Phialophora parasitica is a fungal species with clinical and environmental relevance.
- Accurate identification and understanding antifungal susceptibility are crucial for effective treatment.
Purpose of the Study:
- To compare morphologic and physiologic characteristics of Phialophora parasitica isolates.
- To evaluate the antifungal susceptibility profiles of these isolates.
Main Methods:
- Monoconidial cultures from 12 clinical and environmental isolates were analyzed.
- Morphologic, physiologic (urease, casein, starch, tyrosine, gelatin hydrolysis), and temperature growth profiles were assessed.
- Antifungal susceptibility testing was performed using minimum inhibitory concentrations (MICs).
Main Results:
- Isolates exhibited variability in distinguishing characteristics across different media.
- All isolates were urease-positive, hydrolyzed casein and starch, and most decomposed tyrosine.
- Optimal growth occurred at 23 and 37 degrees C; no growth at 40 degrees C.
- Most isolates showed low sensitivity to amphotericin B and miconazole, and resistance to 5-fluorocytosine and ketoconazole.
Conclusions:
- Phialophora parasitica isolates display diverse characteristics and antifungal responses.
- Amphotericin B and miconazole show potential therapeutic value, while 5-fluorocytosine and ketoconazole are less effective.
- Further comparative studies with related Phialophora species are warranted.