Vol 3 (1) 2011 - UBM :: Departamentul de Chimie-Biologie

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Carpathian Journal of Food Science and Technology 2011, 3(1), 44-56 fast growth of the fish [13]. Tetracyclines such as tetracycline, chlortetracycline, doxytetracycline, and oxytetracycline are probably the most widely used therapeutic antibiotics in human and food-producing animals because of their broad-spectrum activities and cost effectiveness [14]. The number of antibiotics used in fish farming is restricted, but oxytetracycline is probably the most frequently used therapeutic antibiotics in fish farms to treat the bacterial infection and limits the fish mortality, particularly in controlling of Aeromonas hydrophila and A. Salmonicida [15, 16]. The abuse used of the antibacterial drugs in the ecosystem specially, at farm level can be accumulating in Tilapia till reach above the standard permissible limits consequently increase the potential hazards for consumer's health [13]. Antibacterial drugs have the potential to gradually accumulate in the body of the consumers causing certain organs or system malfunction [13] such as disorders in the intestinal flora, hypersensitivity reaction, chronic nephrotoxicity, hepatotoxicity, skin hyperpigmentation in the sun exposed areas, hypouricemia, hypokalemia, proximal and distal renal tubular acidosis, poor fetal development, and secondary tooth discoloration of young children [17]. In addition, the transmission of the resistance gene from the pathogenic and non pathogenic bacteria and in between them to the human through the food chain results in treatment-resistant illness in human [18, 19, 20]. Therefore, this study was conducted to evaluate the safety of farmed Oreochromis niloticus for human consumption through the qualitative and quantitative detection of antibiotics residue levels in fish muscle as well as examine the isolated Aeromonas species for oxytetracycline susceptibilities. 2. Material and Methods 2.1. Samples collection Three different groups of farmed tilapia, Oreochromis niloticus, previously known be treated by oxytetracycline were collected during summer season from fish farms at Port-Said Governorate, Egypt. Dead fish was discard and a total of 180 sample, 60 for each group, as soon as they cough, were separately placed into sealed sterile plastic bag, thoroughly identified and delivered to the laboratory in a refrigerated container for qualitative and quantitative detection of antibiotics residues with the investigation of the Aeromonas isolates for oxytetracycline resistance. 2.2. Detection of Antibiotics residues Antibiotics residues of fish samples were carried out by Agar Disk Diffusion Method according to Myllyniemi [21]. Three flasks of Muller Hinton agar media were prepared according to the manufacturer’s instructions and adjusted to pH 6, 7.2 and 8 then poured in Petri-dish of 90 mm diameter at 45-50 ° C. For each sample, three solidified Muller Hinton agar plates were inoculated with Bacillus subtilis as a test strain. Trimethoprim was incorporated into the pH 7.2 media (plate 2) with a concentration of 0.005 mg/ml to enhance the sensitivity towards sulfonamides residues. The appropriates discs of standard penicillin, sulfamethazine and dihydrostreptomycin were placed in the center of plates 1, 2, and 3 respectively. Fish sample was prepared by cutting and slicing the muscle into 2 mm thickness using cork borer. Six pieces of different muscle samples and one negative control paper disc were placed in each plate at a distance of 10 mm from the plate's edge, and then incubated at 30 ° C for 18 hr. The interpretation of the results depending up on the diameter of the inhibition zone around the samples where, the complete inhibition of the growth in an annular zone around the 45
H. El-Sayed M. Farag, Concentration of antibiotics residues in farmed tilapia and their relationship to resistant Aeromonas strains muscle disc samples measured ≥2 mm wide indicates positive results and detection of certain antibiotic. On the other hand, the diameter of inhibitory zone around the disc samples measured ≥1 to < 2 mm indicates suspicion result while a measured
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Page 12 and 13: K. Otto , T. Mihaela, F. Boltea , L
Page 26 and 27: A. Aberoumand, Investigation of the
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Page 62 and 63: Y. Vagelas , M. Zold, L. Giurgiules
Page 68 and 69: M. Bertrand, M. M. Özcan, Oil yiel
Page 80 and 81: GUIDE FOR AUTHORS The Editor welcom

Vol 3 (1) 2011 - UBM :: Departamentul de Chimie-Biologie

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