Identification of bacterial flora for the Nile Tilapia (Oreochromis niloticus) fillet product sold in fish markets of Jimma, Ethiopia

Abstract

A research exercise was undertaken on isolation and identification of bacteria associated with packed fillets of Nile Tilapia fish (Oreochromis niloticus) sold at Jimma town, Oromia, southwest of Ethiopia since March, 2015 to June, 2015. Tissue sections (fillets) of randomly selected Nile Tilapiafishes were studied upon. A serial dilution up to 104 was carriedout, and studied on nutrient agar. A total of four bacterial families were isolated and identified as Staphylococci, Enterobacteriaceae, Coliform, and aerobic mesophilic bacteria. Out of 73 isolates, 24 isolates were found as Gram positive and 49 were Gram negative; 22 cocci while 51 isolates were identified as rod shaped; 10 isolates were found to have endospore whereas 63 of isolates were non-spore forming bacteria; and 67 of isolates were catalase positive with only 6 catalase negative isolates. The number of colony counted from the plate indicated that Enterobacteriaceae were identified as the highest load (8.92x106CFU/ml), while Staphylococci the least (2.755x106CFU/ml). The mean bacterial load of isolates (6.1x106 CFU/ml) was found to be markedly higher than the recommended public health and standard value (5.0 x 106 CFU/ml) which has been adopted by most countries.