Microbial Causes of Summer Mortality in Farmed Fish in Egypt

Abstract

Bacterial diseases are responsible for sever mortalities and morbidities in cultured Nile tilapia in Egypt in various fresh water fish farms and the increase of water temperature in summer has a significant effect on mortalities. A total number of 100 clinically diseased Nile Tilapia (Orechromis niloticus) were collected alive randomly from Abbassa, Elsharkia (Central Laboratory for Aquaculture Research) Egypt, to identify the bacterial pathogens affect that fish. Samples were isolated from liver, kidney, spleen, eye, ulcer and brain. The isolated fish pathogens were identified as Aeromonas hydrophila, Ps.fluorescense, Ps.putida and V.cholera by their morphological characteristics, biochemical tests, Antibiotic sensitivity test and polymerase chain reaction test as a confirmatory results. The results of Anmicrobial sensitivity of the isolated strains revealed that tetracycline (TE30), oxytetracycline (T30), nalidixic acid (NA30), norfloxacin (NOR10) and sulpha-Trimethoprim (SXT25) were the drugs of choice against Aeromonas hydrophila, tetracycline (TE30),oxytetracycline (T30), tobramicin (TOB10) and kanamycin (K30) were the drugs of choice against Pseudomonas flurocence, streptomycin (S10), tobramicin (TOB10), and kanamycin (K30) were the drugs of choice against Pseudomonas putida While oxytetracycline (T30) and nalidixic acid (NA30) were the drugs of choice against Vibrio cholera. The results of Polymerase Chain Reaction (PCR) confirmed the antibiotic sensitivity test results and also confirmed the incidence of Aeromonas hydrophila, Pseudomonas flurocence and Vibrio cholera in the infected fish.