Survey Of Natural Distribution Of Black Yeasts In Malaysia With Special Emphasize On Exophiala Dermatitidis
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Date
2019-04
Authors
Jayaram, Mehalene
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Black yeasts are ecologically remarkable as they can live in extreme, unusual
and toxic environments. Exophiala dermatitidis, a human opportunistic pathogen was
previously reported to be isolated from sauna facilities, oak sleepers of railway ties,
faeces of frugivorous birds and bats, land contaminated with waste petrol
hydrocarbons and dishwashers worldwide. Cryptococcus neoformans, on the other
hand, was isolated from tree trunk hollows, Eucalyptus trees and faeces of birds. Both
of these yeasts were frequently isolated from tropical regions of the world. As there
are limited reports of environmental isolation of these black yeasts in Malaysia, their
natural distribution in the environment were surveyed in this study. Forty-seven strains
of Exophiala spp. and four strains of Cryptococcus spp. were isolated from various
locations in Malaysia. As Exophiala spp. are dimorphic fungi, the colonies were grown
under different conditions to identify the yeast and hyphal growth of the black fungi.
Urea hydrolysis, DNAse test and proteinase activity were also conducted to test their
physiological properties. The black yeasts were characterised by the type of
conidiogenous cells, and chlamydospores produced and their identity confirmed by
sequencing of the ITS region. Overall, 22 strains of E. dermatitidis were successfully
identified from railway track stones (n = 5), burnt tree bark (n = 2), oil dripped soil
sample (n = 5), hot spring biofilm (n = 1), tar road contaminated with petrol
hydrocarbon (n = 4), pigeon droppings (n = 2), drain and deep mud of Sungai Pinang
(n = 3).
Description
Keywords
Black Yeasts , Exophiala Dermatitidis