Physiological characters of Sporothrix schenckii isolates

Area of Science:

• Medical Mycology
• Infectious Diseases
• Clinical Microbiology

Background:

• Sporotrichosis is a fungal infection endemic to specific regions in India.
• Understanding the etiological agent's characteristics is crucial for disease management.
• Previous studies have not comprehensively analyzed clinical isolates from diverse Indian geographical areas.

Purpose of the Study:

• To characterize the colony morphology and physiological properties of clinical isolates of Sporothrix species from distinct Indian regions.
• To compare the behavior of mycelial and yeast forms of these isolates under various environmental conditions.
• To identify potential geographical variations in the characteristics of Sporothrix isolates in India.

Main Methods:

• Analysis of colony morphology and physiological characteristics of 49 clinical isolates (25 north, 17 east, 7 south India).
• Evaluation of isolates in both mycelial and yeast forms across different media and conditions.
• Testing of growth at varying temperatures (up to 40°C), pH levels (2.4-12.0), osmotic pressures, and salt concentrations.
• Assessment of nutrient assimilation (arabinose, dextrin, raffinose, rhamnose, starch), urease activity, phenol oxidase, potassium nitrate assimilation, gelatinase activity, and casein hydrolysis.

Main Results:

• No significant difference in colony character was observed across the 49 isolates on three different media.
• All isolates showed inhibited growth at 40°C.
• Yeast forms exhibited greater tolerance to osmotic pressure and salt concentrations compared to mycelial forms.
• Mycelial forms grew well between pH 3-12.0, while yeast forms tolerated pH 2.4-9.5.
• Variations in the assimilation of specific carbohydrates (arabinose, dextrin, raffinose, rhamnose, starch) were noted among isolates from different geographical regions.
• Mycelial forms demonstrated urease activity, which was absent in yeast forms.
• Phenol oxidase and potassium nitrate assimilation were consistently positive, while gelatinase activity and casein hydrolysis were negative for all isolates.

Conclusions:

• Geographical origin in India correlates with specific physiological variations in Sporothrix clinical isolates, particularly in nutrient assimilation.
• Distinct tolerance ranges for pH and osmotic stress exist between the mycelial and yeast forms.
• The consistent urease activity in mycelial forms and its absence in yeast forms could be a distinguishing feature.
• These findings contribute to a better understanding of Sporothrix epidemiology and potential strain differentiation within India.