Environmental prevalence of Cryptococcus neoformans and Cryptococcus gattii in India: An update

Abstract

An overview of work done to-date in India on environmental prevalence, population structure, seasonal variations and antifungal susceptibility of Cryptococcus neoformans and Cryptococcus gattii is presented. The primary ecologic niche of both pathogens is decayed wood in trunk hollows of a wide spectrum of host trees, representing 18 species. Overall, C. neoformans showed a higher environmental prevalence than that of C. gattii which was not found in the avian habitats. Apart from their arboreal habitat, both species were demonstrated in soil and air in close vicinity of their tree hosts. In addition, C. neoformans showed a strong association with desiccated avian excreta. An overwhelming number of C. neoformans strains belonged to genotype AFLP1/VNI, var. grubii (serotype A), whereas C. gattii strains were genotype AFLP4/VGI, serotype B. All of the environmental strains of C. neoformans and C. gattii were mating type α (MATα). Contrary to the Australian experience, Eucalyptus trees were among the epidemiologically least important and, therefore, the hypothesis of global spread of C. gattii through Australian export of infected Eucalyptus seeds is rebutted. Reference is made to long-term colonization of an abandoned, old timber beam of sal wood (Shorea robusta) by a melanin positive (Mel⁺) variant of Cryptococcus laurentii that was pathogenic to laboratory mice.

Keywords::

• Cryptococcus neoformans
• Cryptococcus gattii
• natural habitat
• ecological niche
• decaying wood
• India

Acknowledgements

Acknowledgment is made to the Indian National Science Academy, New Delhi, for the award of an Honorary Scientist position to H. S. R. This work was written during a research fellowship of A.C at the Canisius Wilhelmina Hospital, Nijmegen, the Netherlands.

Declaration of interest

This work was financially supported by the Department of Science and Technology, Government of India (F.No.SR/SO/HS-62/2008), the Indian Council of Medical Research, New Delhi (HIV/50/107/2008) and Labland BV, Wijchen, The Netherlands. J.F.M. received grants form Astellas, Merck, Basilea and Schering-Plough. He has been a consultant to Basilea and Merck and received speakers fees from Merck, Pfizer, Schering-Plough, Gilead and Janssen Pharmaceutica. All other authors: no potential conflicts of interest.