الفهرس 
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Abstract
Many drugs are used in livestock farming, particularly antibiotics, with almost 80% of world antibiotic production used for animals. Therefore, veterinary drugs may be present as residues in food of animal origin, the presence of unauthorized substances, residues of veterinary medicinal of their residues in various organs and tissues. Consumption of these residues through meat and products or chemical contaminants in food may pose a risk factor for public health due to deposition meat products may cause direct and indirect toxicity in consumers and results in failure of treatment due to development of resistant microorganisms, the EU legislative framework defines maximum limits permitted in food and monitoring program for the control of the presence of these substances in the food chain. Regulation (EU) No 37/2010 establishes maximum limits for residues of veterinary medicinal products in food-producing animals and animal products.
The aim of our study is to evaluate the antimicrobial residue randomly selected cattles slaughtered in El Dakhla city in different slaughter houses using primary screening Four Plate Test then we confirmed and quantify the results by High Pressure Liquid chromatography and comparing these results with the maximum residual limits instructed by international authorities.
The study lasted from May 2016 till February 2017, two hundred randomly selected slaughtered cattles tested microbiologically for presence of macrolides, tetracyclines, β-lactams, aminoglycosides, and sulfonamides in the laboratory of Animal Health Research Institute a branch of El Dakhla city, Al Waddy Al Gedid
The samples were divided into three groups: -
1-Two hundred (200) muscle samples (from Diaphragm (.
2- Two hundred (200) liver samples.
3- Two hundreds (200) kidney samples.
Antibiotic detection using (FPT); five different inoculated media were used:
1. Medium I; test agar pH 8 seeded with Micrococcus luteus (sensitive for Macrolides and aminoglycosides).
2. Medium II; test agar pH 6 seeded with B.subtilis (sensitive for tetracyclines and beta-lactams).
3. Medium III; test agar pH 6 seeded with E. coli (sensitive for quinolones and fluoroquinolones).
4. Medium IV; test agar pH 8 seeded with B.subtilis (sensitive for aminoglycosides).
5. Medium V; test agar pH 7.2 with trimethoprim seeded with B.subtilis (sensitive for sulfonamides).
According to the data obtained in the present study, it appeared that the incidence of antibacterial drug residues in slaughtered cattle were 6%, 14.3% and 11.6% in muscle, liver and kidney samples respectively and the samples were higher in β-lactam and tetracyclines (23.83% with 0.83% suspected result) especially in kidney 33% (66/200) followed by aminoglycoside (15.2% with 3% suspected) then Sulfonamide (8.66% with 1.16% suspected) and macrolides (4.66% with 1.33% suspected) finally quinolone and fluoroquinolone which shown zero percent in muscle samples, recorded 0.83% positive (5/200) with 2.16% suspected result.
HPLC analysis
Throughout 143 samples were positive in FPT there were 46.66% oxytetracycline residues and 13.33% penicillin G residues using HPLC above the EU Commission Regulation 37/2010.
Antibacterial drug residues in the examined samples recorded 80% in muscle, 60% in liver and 40% in kidney.
Oxytetracycline was more prevalent than penicillin-G residues, oxytetracycline (46.66% of 75 tissue samples) while penicillin (13.33% of 75 tissue samples ).
The study recorded that oxytetracycline residues has the higher level in muscle (80%) then liver (40%) and kidney (20%) while muscle recorded zero penicillin G residues and each of liver and kidney recorded (20%).
Throughout three suspected samples (one of each muscle, liver and kidney) for oxytetracycline there were two positive samples (muscle and liver).
Analysis indicated that beef sold in El-Dkhala was found to be with high levels of antibiotic residues as compared to other studies. Beef contamination by antibiotics may pose a health threat to consumers in the New Valley Governorate. Strict regulation on the use of antimicrobial drugs in the livestock sector is required.