Differentiation between Trichophyton mentagrophytes and T. rubrum by sorbitol assimilation

Area of Science:

• Medical Mycology
• Clinical Microbiology

Background:

• Trichophyton rubrum and Trichophyton mentagrophytes are common dermatophytes causing superficial fungal infections.
• Accurate differentiation between these species is crucial for effective treatment and epidemiological studies.
• Traditional methods for differentiating these species can be time-consuming and may lack specificity.

Purpose of the Study:

• To evaluate the utility of sorbitol assimilation as a rapid and reliable method for differentiating Trichophyton rubrum from Trichophyton mentagrophytes.
• To establish a clear diagnostic criterion based on sorbitol assimilation for these two key dermatophyte species.

Main Methods:

• Utilized the API 20C AUX identification system to assess the metabolic capabilities of fungal isolates.
• Tested a collection of 36 confirmed Trichophyton rubrum strains and 147 confirmed Trichophyton mentagrophytes strains.
• Assessed the ability of each strain to assimilate sorbitol, a key carbohydrate substrate.

Main Results:

• All 36 strains of Trichophyton rubrum demonstrated positive assimilation of sorbitol.
• None of the 147 strains of Trichophyton mentagrophytes assimilated sorbitol.
• Sorbitol assimilation provided a clear and distinct separation between the two species.

Conclusions:

• Sorbitol assimilation is a highly effective and simple method for differentiating Trichophyton rubrum from Trichophyton mentagrophytes.
• The API 20C AUX system, specifically the sorbitol assimilation test, offers a valuable tool for routine clinical mycology laboratories.
• This method enhances diagnostic accuracy and facilitates timely patient management for dermatophytosis.