الفهرس 
ACKNOWLEDGEMENT
Detection of antimicrobial residues in chicken meatOnly 14 pages are availabe for public view
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Abstract
Residues of veterinary drugs in food have received much attention in recent years because of growing food safety concerns. There are serious effects of antibiotics residues in chicken meat for human consumption (e.g., increase antimicrobial resistance, carcinogenicity, mutagenicity, and hypersensitivity). The presence of antibiotic residues and their associated harmful health effects on humans make the control of veterinary drug residues an important measure in ensuring consumer protection.
The main objective of this study was to evaluate the presence of some antimicrobial residues in chicken meat served in Assiut City with quantification of the residues and comparing the results with maximum residue limits instructed by international authorities.
The study lasted from March 2015 till May 2016. Two hundred thirty five chicken meat samples were collected from different markets distributed over the study area. All samples were tested for the presence of β-lactams, tetracyclines, sulfonamides, aminoglycosides, macrolides and quinolones (as groups).
The samples were divided into three groups:-
1- Twenty six (26) local broiler chicken carcasses subdivided into:-
a- Thirteen (13)fresh broiler chicken carcasses weighing 1.8: 2 kg and represented by 3 samples (13 breast muscle, 13thigh muscle and 13liver) (n=39).
b- Thirteen (13) frozen broiler chicken carcasses weighing 1: 1.2 kg and represented by 2 samples (13 breast muscle and 13 thigh muscle) (n=26).
2-One hundred and forty (140) local frozen chicken cuts (70 chicken breast and 70 chicken thigh).
3- Thirty (30) local frozen chicken liver.
The strategy for residue detectionincluded qualitative method using microbiological screening method; four plate test (FPT)followed bythe second step which was confirmation of the positive samples and quantification of the residues by using HPLC.
Firstly in four plate test (FPT); five different inoculated media were used for antibiotic detection:
1-Medium I; test agar pH 6 seeded with B.subtilis (sensitive for tetracyclines and beta-lactams).
2-Medium II; test agar pH 7.2 with trimethoprim seeded with B.subtilis (sensitive for sulfonamides).
3-Medium III; test agar pH 8 seeded with B.subtilis (sensitive for aminoglycosides).
4- Medium IV; test agar pH 8 seeded with Micrococcus luteus (sensitive for Macrolides and aminoglycosides).
5- Medium V; test agar pH 6 seeded with E. coli(sensitive for quinolones and fluoroquinolones).
After obtaining the primary screening results by FPT, HPLC technique was used for more identification and quantification of the suspected residues on the basis of their retention times (RTs) as compared to the standards and by adding known quantities of the standards to the samples and re-chromatography which showed complete overlap of analyte peaks.
This study revealed that the antimicrobial drug residueswere detected in18 (7.66%) out of 235 different examined chicken tissue samples.
The highest levels were for macrolides (tylosin, 3.82%), followed by sulfonamide antibiotics (sulfadimidin, 2.55%) and finally tetracycline group (doxycycline, 1.28%).All 235 examined samples were free from aminoglycosides and quinolones residues.
The incidence of antibiotic residues was in local fresh carcasses (4 out of 39 samples with a percentage of 10.26%) while, local frozen carcasses didn’t show any residues at all.Local thigh cuts showed (8 out of 70 samples with a percentage of 11.43%) which was higher than breast cuts (2 out of 70 samples with a percentage of 2.86%). In local frozen liver (4 out of 30 samples with a percentage of 13.3%) were recorded positive.
Thirteen (72.2%) out of 18 HPLC examined samples for different antimicrobial drug groups had residues above the permissible maximum residue limits (MRLs) in comparison withthe permissible limits recorded by EU Commission Regulation No.37/ 2010.
The mean value of doxycycline residues in thigh meat was 439.69µg/kg.The mean values of sulfadimidin residues in breast meat were 709.3µg/kg while in thigh muscle was 22.45µg/kg. While, the mean values of tylosin residues were 576.38, 774.6and 1722.3µg/kg for local fresh carcasses, thigh and liver, respectively.
In conclusion, the obtained results in this study confirmed the presence of antibiotic residues in poultry meat samples collected from Assiut City. This may pose potential hazard to public health. Thus, it is recommended that rules should be taken to ensure observing proper withdrawal periods before marketing and drug control in veterinary use. In addition, a monitoring policy should be implemented to ensure the conformity of poultry meat sold in Assiut City with international standards.