Pathogenicity of Exophiala xenobiotica isolated from infected Crocodile fish for Rabbit fish Siganus rivulatus (Forsskål, 1775)

Abstract

In our study, we isolated 49 isolates belonging to three species and four genera from infected Crocodile fish (Cymbacephalus beauforti) collected from Hurghada, Red Sea. Of the few fungi isolated; (Cladosporium cladosporioides, Aspergillus versicolor, Exophiala and Rhodotorula sp.). The black yeast was identified by molecular sequence analysis of the internal transcript spacer (ITS) region of the ribosomal RNA gene. After sequencing the internal transcribed spacer domain, the fungus was identified as Exophiala xenobiotica and it was selected to infect an economical fish (Rabbit fish; Siganus rivulatus). Pathogenicity test showed a highly systematic infection of the liver and kidney of Rabbit fish. Histology revealed granulomatous infiltration containing septate, brown-colored dematiaceous hyphae in the liver and kidney while gills showed high damage with no lesion in the skin.