Asian Journal of Microbiology, Biotechnology & Environmental Sciences Paper

USING EXPRESSION OF IMMUNE RESPONSE GENES AND HISTOPATHOLOGICAL CHANGES IN TILAPIA ZILLI AS A BIOMARKER TO BACTERIAL INFECTION IN LAKE QARUN

SALLY S. ALAM, HEBA A.M.ABD EL-KADER, SHEREIN I. ABD EL-MOEZ, NEVIEN M. SABRY, AMANY M. KENAWY AND KARIMA F. MAHROUS

Abstract

The excessive contamination of aquatic ecosystems has evoked major environmental and health concerns worldwide because the aquatic environment makes up the major part of our environment and resources. Qarun Lake is one of the most vulnerable areas. So fish samples from this area were inspected for the presence of pathogenic bacteria. In this study a total of 60 samples of fish Tilapia zilli were collected from Qarun Lake for bacteriological, histopathological and molecular examination. Three different types of pathogenic bacteria (Aeromonas hydrophila, Flavobacterium Columnares and Pseudomonas fluorescens) were isolated from different tissues of 23 infected fish. The results of bacteriological examination revealed the occurrence of 17 isolates of Ps. fluorescens, 11 isolates of A. hydrophila and 8 isolates of F.columnare; respectively which was confirmed using Polymerase Chain Reaction (PCR) technique. Regarding to gene expression analysis using RT-PCR technique in natural and pathogenic Tilapia zilli, the results showed that the hepicidin expression was found in all normal tissues of liver, kidney, gills and intestine while in infected tissues the highest expression level was observed in the gills followed by liver, intestine and kidney and the expression level of (TH2-3) was higher than (TH2-2) and (TH1-5). Histopathological studies on pathogenic Tilapia zilli detected significant changes in the fish skin and degenerative changes in the internal organs especially liver, kidney, spleen, gills and intestine. It was concluded that hepicidin is involved in the innate immunity of T. zilli and probably as an important effective component in specific tissues in response to invading microorganisms and bacterial infections were linked with numerous pathological changes.