Cluster Analysis of Aerobic Heterotrophic Bacteria from Clarias gariepinus and Tilapia zillii in Unwana River, Ebonyi State, Nigeria
Abstract
Fish is a major source of protein for humans, and it is patronized by many in the tropics – where fishes can either be cultivated in the farms domestically or caught from open water bodies such as rivers, ponds and streams. These various sources of fishes and their attendant diversity of microorganisms particularly the bacteria make fishes as potential sources of pathogens. The maintenance of the microbiological quality of food and water is important to prevent waterborne/foodborne diseases in any community, thus the need for this study. A total of 14 samples of water at different points (upstream, midstream and downstream) and 50 samples of live fish es were used for this study. Each of the fish sample was bacteriologically analyzed using the pour -plate and spread plate techniques on culture media plates. And the isolated bacteria were identified using standard microbiological identification techniques . The water samples were subjected to physicochemical analysis to determine the physical and chemical properties of the water. The relatedness of the isolated bacteria was established using cluster analysis/dendogram. The highest bacterial count was obtain ed from downstream water sample (5.6x10 cfu/ml), indicating a possible pollution of water at this point. Both aerobic heterotrophic Gram positive and Gram negative bacteria were isolated. The Gram positive bacteria isolated include Staphylococcus lugdunens is, S. hominis, S. cohnii, Streptococcus pyogenes, S. pneumoniae, Kocuria varians while the Gram negative bacteria include Raoutella ornithinolytica, Klebsiella pneumoniae, Aeromonas hydrophila, A. veronii, Proteus vulgaris, Serratia fonticola, and Enterob acter gergoriae. Cluster analysis using dendrogram showed some degree of similarity among the different clusters of isolated bacteria. The result of this study presumptively shows that the water sample is polluted; and this in turn affects fresh water fish es in the river. Therefore the microbiological examination of the water at this study site is necessary for monitoring and controlling the quality and safety of the water for usage by the locals.
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Introduction
World Fish Centre showed that about 80 to 90 million people depend solemnly on fish annually as their main source of protein (World Fish Centre, 2002). Fishes have been described as the most important animal protein food available in the tropics (Ali et al., 2008). About 40% of the dietary protein intakes of an average Nigerian are sourced from fish (Federal Department of Fisheries, 2007). The most commonly cultivated species of fish in Nigeria include catfish, tilapia and carp, and about 60 % of the people leaving in most developing countries depend on fish as their own source of protein (Olagunju et al., 2007; FAO, 2003). Proteins obtained from fish contain essential amino acids and have good cholesterol and also low cholesterol level in the body (Anthonio and Akinwumi, 1991, Fagbenro and Arowosoge, 1998). Proteins derived from fish have been of economic value in Africa especially in less developed or developing areas where other sources of animal protein are scarce and expensive (FAO, 2003). Water quality greatly influences the aquatic environment and is important for the survival of aquatic flora and fauna (Deekae et al., 2010). The entire array of aquatic life and water quality are affected by pollution. Human activities and anthropogenic pressures like industrial, community waste disposal, heavy use of insecticides, pesticides and fertilizers in agricultural practices are major causes of pollution in aquatic environment. Studies have shown that the leading heterotrophic and aerobic bacterial flora content of streams and rivers comprises of mostly the Gramnegative rods which include Aeromonas, Pseudomonas and Enterobacteriaceae and some Gram-positive spore-bearing rods especially those of the genus Bacillus (Rheinheimer, 1985, Olayemi, 1994). Unwana River is a fresh water body in Afikpo North Local Government Area of Ebonyi State, South East of Nigeria. There is paucity of information on the water quality and microflora of fresh water fishes from Unwana River. However, indigenous fishes like Tilapia zillii and Clarias gariepinus are widely harvested locally and are easily available in the local markets of Uwana community. This study was therefore aimed at studying the water qualities of Unwana River and its influence on the abundance and diversity of bacteria being harbored both in the water and the resident fishes especially Tilapia zillii and Clarias gariepinus. Also cluster analysis of these isolates was studied.