The environmental source of emerging Apophysomyces variabilis infection in India

Area of Science:

• Mycology
• Environmental microbiology
• Medical mycology

Background:

• The Apophysomyces species complex is a significant cause of mucormycosis in India, second only to Rhizopus arrhizus.
• The environmental sources of Apophysomyces species remain largely unknown, hindering effective control strategies.

Purpose of the Study:

• To investigate the presence and prevalence of the Apophysomyces species complex in Indian soil.
• To characterize the genetic diversity and antifungal susceptibility of isolated Apophysomyces species.

Main Methods:

• Environmental soil samples from diverse Indian geographical locations were analyzed for Mucorales isolation.
• Molecular identification using internal transcribed spacer (ITS) and 28S (D1/D2) ribosomal DNA sequencing.
• Genomic diversity assessed via amplified fragment length polymorphism (AFLP) fingerprinting.
• Antifungal susceptibility testing to determine minimum inhibitory concentrations (MICs) for key antifungal agents.

Main Results:

• Apophysomyces species complex was isolated from 4.5% of soil samples, significantly associated with low soil nitrogen content.
• Isolates were identified as Apophysomyces variabilis, exhibiting 98-100% sequence similarity to the type strain.
• AFLP analysis revealed considerable genomic diversity among A. variabilis isolates, forming multiple clades.
• A. variabilis isolates demonstrated relatively high minimum inhibitory concentrations (MICs) for amphotericin B.

Conclusions:

• Apophysomyces variabilis is prevalent in Indian soils, particularly those with low nitrogen content.
• The identified genetic heterogeneity of A. variabilis suggests complex population dynamics.
• The observed high MICs for amphotericin B highlight potential challenges in treating Apophysomyces-associated mucormycosis.