Consistent high prevalence of Exophiala dermatitidis, a neurotropic opportunist, on railway sleepers

We examined 150 railway samples using cotton swabs moistened with sterile physiological saline. Black yeasts and relatives were selected on theirs colony morphology and identified based on ITS rDNA sequencing. Overall, 36 (24%) of samples were positive for black yeast-like fungi, i.e., Exophiala dermatitidis (n =20, 55.6%) was predominant, followed by E. phaeomuriformis (n =9, 25%), E. heteromorpha (n =5, 13.9%), and E. xenobiotica (n =2, 5.6%). Massive contaminations of E. dermatitidis were seen on railway sleepers on creosoted oak wood at the region close to the sea level, while in cold climates were primarily contaminated with clinically insignificant or rare human opportunists (E. crusticola). It seems that, high temperature and humidity are significant effect on species diversity. Moreover, the MIC results for all E. dermatitidis and E. phaeomuriformis strains revealed the widest range and the highest MICs to caspofungin (range 1–16mg/L, Geometric mean 4.912mg/L), and the lowest MIC for posaconazole (0.016–0.031mg/L, G mean 0.061mg/L). However, their clinical effectiveness in the treatment of Exophiala infections remains to be determined.
Source: Journal of Medical Mycology - Category: Biology Source Type: research