Aquaculture sector in Egypt has demonstrated a remarkable development; however, it has also faced challenges with respect to disease outbreaks. Nile tilapia is the most widely cultured species in Egypt. Under stress conditions, tilapia is vulnerable to a variety of bacterial diseases that tend to be ubiquitous in the freshwater environment. Semi-intensive Nile tilapia farms in Kafr El-Sheikh Governorate, Egypt are experiencing acute mortality especially during summer months. The samples from these farms were collected and subjected to investigations to identify the etiological agent(s) behind these mortalities. Bacteriological examination revealed that the dominant bacteria were Gram-negative rods and identified as Aeromonas spp. through biochemical tests. PCR, restriction fragment length polymorphism (RFLP) assays, and sequencing confirmed the presence of Aeromonas hydrophila. In addition, the aerA gene, a virulence factor in A. hydrophila, was detected by PCR in all identified A. hydrophila isolates. In order to confirm that the isolated A. hydrophila was the causative agent of tilapia mortality, healthy Nile tilapia were challenged with the isolated strains, which produced the same clinical picture of the collected samples. This study implicates that A. hydrophila could be the causative agent of the summer mortality in Nile tilapia farms in Kafr El-Sheikh Governorate, Egypt.
The food industry and the frozen fish sector in particular have benefitted greatly from advancements in food processing technologies. This study investigated the effect of adding natural antioxidants such as rosemary and thyme oil to frozen fillets of Nile tilapia (Oreochromis niloticus) in order to preserve their quality for consumers. Fillets were treated with rosemary and thyme at two concentrations (1% and 1.5%) and then were stored at 4°C. Samples were analyzed over 4 days for bacteriological (aerobic plate count, psychotropic count, and coliform count), chemical (determination of pH, thiobarbituric acid reactive substances-TBARS, and total volatile base nitrogen-TVB-N), and sensory quality examination (color, texture, and odor). Significant differences (P<0.05) were observed among different groups in terms of aerobic plate count, psychotropic count, and coliform count during the storage. Moreover, pH, TVB-N, and TBARS mean values in the treated groups were lower than those in the untreated group. The best sensory quality was obtained at the highest concentrations (1.5%) of thyme and rosemary oil.
Owing to the increasing importance of fish as one of the most important food staffs, and constitutes the chief source of protein in the diet of wide range of peoples, and also owing to the wide spread distribution of mould and yeasts which comprise a large group of microorganisms and may contaminate foods, resulting in serious effects on human health. the present study was planned to detect the incidence of mould and yeasts contamination of fresh water fish (Tilapia nilotica) in El-Gharbia and Kafr El-Sheikh Governorates. A total of 180 random samples of (Tilapia nilotica) were collected from El-Gharbia and Kafr El-Sheikh (90 of each) the obtained results indicates that 44.4% and 50% of El-Gharbia and Kafr El-Sheikh samples were contaminated by mould and yeasts respectively. Moreover, the isolated strains of mould and yeasts were identified and recorded in different percents. The public health significance of isolated microorganisms were also discussed.
A total of 90 random samples from frozen beef, poultry and fish (30 of each) were collected from different supermarkets at different localities in Kafr-El Shiekh Governorate. The samples were examined for detection of Aeromonas species using two different selective media. Results obtained on Ampicillin Dextrine Agar revealed that the log mean of Aerom-
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