Possible primary ecological niche of Cryptococcus neoformans

Area of Science:

• Mycology
• Environmental Microbiology
• Infectious Diseases

Background:

• Cryptococcus neoformans is an opportunistic fungal pathogen causing cryptococcosis.
• Natural habitats of C. neoformans are crucial for understanding its epidemiology.
• Tree hollows represent potential microhabitats for fungal survival and dissemination.

Purpose of the Study:

• To investigate living tree hollows as natural reservoirs for Cryptococcus neoformans in an endemic region of Brazil.
• To identify the presence and distribution of C. neoformans varieties within these microhabitats.
• To determine the potential for colonization and long-term survival of C. neoformans in tree hollows.

Main Methods:

• Decaying wood samples were collected from 32 living tree hollows in northeastern Brazil.
• Samples were cultured on niger seed agar for fungal isolation.
• Morphological, physiological, and biochemical tests, including Canavanine-glycine-bromothymol medium and Crypto Check Iatron Kit, were used for identification and serotyping.

Main Results:

• Cryptococcus neoformans was recovered from 18.5% (6/32) of the sampled tree hollows, with 123 colonies identified.
• Both C. neoformans var. neoformans and C. neoformans var. gattii were detected, occurring individually or together in the same hollow.
• Significant fungal loads (0.15-21.7 x 10(3) cfu/g) and long-term presence (19-36 months) were observed in specific tree species (pink shower, fig, pottery trees).

Conclusions:

• Living tree hollows, particularly those of pink shower, fig, and pottery trees, are confirmed natural habitats supporting C. neoformans colonization.
• The concurrent presence of C. neoformans var. neoformans and C. neoformans var. gattii in the same biotope suggests potential interactions and a shared natural niche.
• These findings contribute to understanding the ecological dynamics and life cycle of C. neoformans in nature.