الفهرس 
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Abstract
Nowadays there is increasing in the using of antibacterial drugs in the poultry farms without control; this using not only for protection or treatment but to increase the growth rates to get much money by illegal ways. Recent studies proved that these residues have many hazards if consumed by man.
The existence of these residues may pose a health threat to consumers in varying degrees depend on the type of food and the amount of the residue. Among them are sensitivity to antibiotics, allergic reaction, imbalance of intestinal micro-flora, carcinogenicity, mutagenicity, bacterial resistance to antibiotics in microorganisms and losses in the food industry. Therefore, 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.
So, the main objective of this study was to evaluate the presence of some antibiotic residues in chicken meat served in Assuit city with confirmation and quantification of the positive results by HPLC, comparing antibiotic residues in different types of chicken meat (fresh, local and imported frozen), comparing the results with maximum residue limits instructed by international authorities and determination the effect of cooking processes (boiling and frying) on antibiotic residues naturally incurred chicken muscle.
The study lasted from September 2017 till December 2017. One hundred and twenty chicken meat samples (fresh, local and imported frozen chicken samples (40 of each) which subdivided into (15 breast muscles, 15 thigh muscles and 10 liver samples) were randomly collected from different chicken shops and supermarkets distributed over the study area. All samples were tested for the presence of β-lactams, aminoglycosides, tetracyclines, sulfonamides, macrolides, quinolones and fluoroquinolones.
The strategy for residues detection included two ways:-
1- Qualitative method using microbiological screening method; four plate test (FPT).
2- Quantitative method for confirmation of the positive samples and quantification of the residues by using HPLC.
Firstly in four plate test (FPT); for different inoculated media were used for antibiotic detection:
1- Medium I : test agar (standard II nutrient agar) adjusted at pH 6.0 + 0.1 ml of the B.subtilis BGA spore suspension for detection of β-lactam and tetracycline residues.
2- Medium II: plate culture of B.subtilis BGA spore suspension adjusted at pH 7.2 for detection of sulpha drug residues.
3- Medium III: plate culture of B.subtilis BGA spore suspension adjusted at pH 7.2 for detection of aminoglycoside residues.
4- Medium IV: test agar adjusted at pH 8.0 + 0.1 ml of 24 hours brain heart infusion broth culture of M. luteus ATCC 9341 for detection of macrolide and aminoglycoside residues.
5- Medium V: test agar adjusted at pH 6.0 + 0.1 ml of E.coli tryptone soya broth culture for detection of quinolone and fluoroquinolone residues.
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-chromatograph which showed complete overlap of analyte peaks.
These percentages were:
This study revealed that the antimicrobial drug residues were detected in 22 (18.3%) out of 120 different examined chicken tissue samples.
The incidence of antibiotic residues in fresh carcasses was 10 out of 40 samples with a percentage of 25%, while in local frozen carcasses was 8 out of 40 samples with a percentage of 20% and finally in imported frozen chicken samples was 4 out of 40 samples with a percentage of 10%.
On the other hand, results reported that the incidence of positive samples for antibiotic residues of different parts of chicken carcass (breast, thigh and liver) of all samples by using HPLC system which were 8.3%, 3.3% and 6.7% of breast muscles, thigh muscles and liver samples, respectively.
Moreover, the present data investigated that breast muscles were contaminated with 2.2% for each of tetracycline, aminoglycoside and sulfonamide residues, respectively while 6.7% for macrolides and 8.9% for quinolones. Thereafter, the thigh samples contaminated with 6.7% and 2.2% for aminoglycosides and macrolides, respectively. Finally, results proved that liver samples were contaminated with 10% for tetracyclines, 6.7% for each of sulfonamides and quinolones and 3.3% aminoglycosides.
Quinolones group (norfloxacin) is the most commonly detected antibiotic group 6 (5%) followed by aminoglycosides (gentamicin) 5 (4.2%) then tetracyclines (doxycyclin) and macrolides (tylosin) 4 (3.3%) and the least detected group was sulpha drugs (sulfadimidine) 3 (2.5%). All samples were negative for β-lactams group.
12 (10%) out of 120 examined samples for different antimicrobial drug groups had residues above the permissible maximum residue limits (MRLs) in comparison to the permissible limits recorded by EU Commission Regulation No.37/ 2010.
The mean value of doxycycline residues in breast and liver samples was 103.5 and 296.1µg/kg, respectively, also, in local frozen and fresh samples, respectively. While , the mean value of sulfadimidine residues in breast and liver samples 375 and 173.85 µg/kg, respectively and also, in local frozen and fresh carcasses, respectively.
Adding to that, the mean value of gentamicin residues in breast, thigh and liver samples was 98.54, 106.98 and 198.3 µg/kg, respectively while, 165.05 and 95.89 µg/kg in fresh and local frozen samples, respectively. But, the mean value of norfloxacin residues in breast and liver samples was 50.575 and 137 µg/kg, respectively also, 114.47 and 44.3 µg/kg in fresh and local frozen samples, respectively. Finally, the mean value of tylosin residues in breast and thigh samples was 90.27, 127.4 µg/kg, respectively, also, 99.55 µg/kg in imported frozen samples.
After making heat treatment to positive samples as boiling at 100 ºC for (24 minutes in muscles and 9 minutes in liver) or frying at 200 ºC for 10 minutes in sunflower oil. The obtained results in this study demonstrated that significant decrease of antibiotic residues were detected after boiling and frying processes by HPLC.
The result of the current study declared that the reduction percentage of boiling was 10, 22.2 and 35.64% in breast, thigh and liver tissues, respectively. While in boiling fluid was 8.85, 13.2, 61.85% in breast, thigh and liver tissues, respectively. Also, in frying was 12.1, 43.8 and 61.4% in breast, thigh and liver tissues, respectively.
Finally, the achieved results in this study confirmed the presence of antibiotic residues in poultry meat samples collected from Assuit city. This may pose potential hazards 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.
In addition, proper cooking of poultry meat to reduce residues of antibiotics and the exposure to residues may be reduced by discarding any juices which come from the chicken meat as they are cooked.