PHENOTYPIC AND MOLECULAR IDENTIFICATION OF YEASTS ISOLATED FROM CULTURED TILAPIA (Oreochromis niloticus) IN KAFRELSHEIKH PROVINCE, EGYPT

Abstract

The present study aimed to identify yeasts by phenotypic, biochemical and genotypic methods. Three hundred live Oreochromis niloticus samples were collected from different locations at Kafrelsheikh Governorate, Egypt and during different seasons. Yeast isolates were identified according to their phenotypical characterization in combination with polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) method. Two hundred and twenty-six yeast isolates from eighty diseased and two hundred and twenty apparently healthy O. niloticus samples. Isolated yeasts were Rhodotorula spp. (18.14%), Candida albicans (19.47%), Candida parapsilosis (16.37%), Candida guilliermondii (14.6%), Candida inconspicua (8.85%), Trichosporon asahii (17.25%), Geotrichum spp. (2.66%) and unidentified Ascus forming yeasts (2.66%). Yeasts most frequently isolated from gills and skin. Phenotypic methods are valuable in identification of yeasts into genera but these methods take more time. Molecular methods through the amplification of (internal transcribed spacer) ITS1-5.8S-ITS2 regions of fungal rRNA, followed by RFLP-PCR using Msp1 restriction enzyme allowed simple, rapid, cost-effective, sensetive and accurate identification of the phenotypically identified yeasts. Key words: Oreochromis niloticus; yeast; PCR; Msp1; PCR-RFLP