Antimicrobial screening of commercial eggs and determination of tet

International Journal of Poultry Science 9 (10): 959-962, 2010ISSN 1682-8356 Asian Network for Scientific Information, 2010 Antimicrobial Screening of Commercial Eggs and Determination of
Tetracycline Residue Using Two Microbiological Methods
Bacterial Research Division, National Veterinary Research Institute, Department of Veterinary Public Health and Preventive Medicine, Department of Veterinary Surgery and Medicine, Ahmadu Bello University, Zaria, Nigeria Department of Veterinary Public Health and Preventive Medicine, University of Abuja, Nigeria Abstract: Thirty commercial layer farms were surveyed to obtain information on drug use and to screen eggs
for antimicrobial residues. Tetracycline residue was specifically tested using a commercial test kit. The study
indicated that up to a third of farmers (33.3%) were not adhering to the recommendation on drug use and
thereby allowing drug residues in eggs. Of the 900 commercial eggs screened, 3.6% tested positive for
antimicrobial residues but only 0.1% tested positive for tetracycline residue. The low level of tetracycline
residue detected in this study is an indication of the declining use of this antibiotic in the poultry industry
perhaps due to the increasing availability of cheaper alternatives. There is a need for strict regulation of
veterinary drug in order to guarantee food safety and effective use. To ensure compliance with drug use in
Nigeria, routine surveillance must be conducted using simple detection methods.
Key words: Antimicrobials, commercial eggs, residues, tetracycline
INTRODUCTION
Baker and Leyland, 1983; Blomquist and Hannigren, Majority of food-producing animals receive medication 1966). Tetracycline in meat may potentially stain the for part or most of their lives (Lee et al., 2001).
teeth of young children. Penicillin in chicken was Antimicrobials particularly tetracycline are routinely reported to have caused severe anaphylactic reaction in added to animal feed at sub therapeutic levels for their a consumer (The and Rigg, 1992). Skin allergies in growth promoting properties (Droumev, 1983; Kabir et eggs containing sulfonamide residues have also been al., 2004). Antimicrobials are also used for the treatment of food animals especially poultry (Johnston, 1998). The Veterinary drugs are sold in the open market in Nigeria.
increased demand for eggs by the growing fast food In a bid to reduce the cost of veterinary services, some industry in Nigeria and the consumption of eggs as a farmers purchase drugs from the market without sound source of animal protein places a lot of pressure on the diagnostic advice leading to the abuse and misuse of drugs. An official monitoring programme on drug indiscriminately to boost production with farmers failing residues is lacking in Nigeria and consumer response to observe the recommended withdrawal periods.
toward the dangers posed by residue is passive (Kabir The misuse of antimicrobial agents in food animals has et al., 1999). In this study, a survey was conducted to become a very important public health issue. The abuse assess drug use amongst poultry farmers, detect the or misuse of veterinary drugs is one of the causes of presence of antimicrobials and in particular tetracycline drug residues in animal products (Salehzadeh et al., 2006; Pavlov et al., 2008). Information on the effects ofantimicrobial residues in human in Nigeria is scanty, MATERIALS AND METHODS
although NAFDAC in 1996 reported the mutagenic Sampling commercial chicken eggs: Thirty commercial
potentials of nitrofuran drugs used in the treatment of poultry farms were selected using stratified random Salmonella in poultry. The human health problems that sampling method. Information on drug use was could result from the intake of sub-therapeutic exposure collected using two different structured questionnaires of tetracycline include gastrointestinal that were distributed to both farmers and veterinary disturbances, poor foetal development, hypersensitivity personnel. Also clinical observations on the farms were reactions and other toxic effects (Stowe et al., 1980; noted and recorded. All crates of eggs available at the Corresponding Author: Fagbamila Idowu, Bacterial Research Division, National Veterinary Research Institute, P.O. Box 01, Vom,
Int. J. Poult. Sci., 9 (10): 959-962, 2010 selected farm were assigned numbers. The egg at the and 8.76 g Sodium chloride at 150 mM. This was then top left corner of the first crate was assigned No.1 and adjusted to a pH of 7.5 using Sodium hydroxide.
the last egg in the bottom right corner assigned No.30.
Numbering was continued with No. 31 at the top left corner of the second crate in that order to the last egg A total of 32 (3.6%) eggs from 10 (33.3%) farms tested according to the method used by Kabir et al. (2004).
positive for antimicrobials using the disc diffusion test.
Nine hundred (900) eggs (30 eggs per farm) were When tested with the commercial test kit, only 18 (2%) selected using a simple random sampling method eggs samples from 10 (33.3%) gave positive results.
without replacement. The eggs were arranged in a clean Only one (0.1%) gave a positive result for tetracycline.
container and transported to the laboratory immediatelyfor processing or refrigerated at 4 C till the following day.
Farmers perception of dangers of drug residues:
Eighty five (85) of the 110 questionnaires distributed to
Testing of eggs for antimicrobial residues: The
farmers were returned representing a total of 77.3% antimicrobial screening of eggs was carried out using responses. The educational status of the farmers showed that 6 (7.1%) of the respondents have primary stearothermophilus C-953 (DSM, Netherlands) was school education, 17 (20%) have secondary school used as the test organism (Anakalo and Kihumbu, education while 62 (72.9%) have tertiary level education.
2005). An 18 h culture of the test organism in 10 ml The study showed that there were no significant nutrient broth (Oxoid Basingstoke, Hampshire, UK) was differences (p>0.05) between the frequency of drug used to inoculate Mueller Hinton agar plates. The egg administration and the experience of poultry farming.
surface was thoroughly cleansed using sterile cotton Twenty six (30.6%) of respondents had flock sizes less wool soaked in 70% alcohol. Sterile forceps were used than 500 birds, 40 (47.1%) had between 500-2,000 birds to puncture the egg at the tip to create a small opening while 19 (22.4%) had over 2,000 birds. Fifteen (17.7%) from where the albumen was carefully drained out of the respondents kept only broilers, 59 (69.4%) kept leaving behind the yolk which was transferred into a only layers while 11 (12.9%) kept both broilers and sterile beaker and thoroughly homogenized. Half of the layers. Eighty one (95.3%) of these farms were on deep homogenized yolk was transferred into a transparent litter system while 4 (4.7%) used battery cages. Seventy sterile bottle and properly labeled before refrigerating at five (88.2%) of the farmers had veterinarians who consulted for them. Eighty two (96.5%) of respondent Sterile filter paper disc 0.6 cm in diameter was dipped treated their birds with antimicrobial agents while sixty into the other half of the homogenized egg yolk and three (74.1%) were aware of drug residues in animal placed gently on the Mueller Hinton agar plate that has products. There was no significant (p>0.05) association already been inoculated with the test organism between the educational status of the farmers and their according to the method of Shahid et al. (2007). This awareness about antibiotic residues in poultry. Seventy was then incubated at 37 C for 24 h after which th four (87.1%) were concerned about antibiotic residues plates were viewed for the presence or absence of in poultry and poultry products treated soon before zones of inhibition of the test organisms around the test slaughter. Sixty six (77.6%) of the respondents thought and control discs. The difference between the diameter antibiotic drugs were being misused or abused. This of zone of inhibition and that of the disc were calculated.
was blamed on quacks and fellow farmers. 89% of Any disc with a difference of 1 mm or more was respondents were aware of withdrawal period of considered positive for the presence of antimicrobial antimicrobial drugs but up to a third (32%) did not The positive samples were further tested using acommercial test kit (Premi®Test Kit, DSM, Netherlands).
Veterinary professional perception of drug residues:
The stored homogenized egg yolks that were positive Thirty nine of the 55 questionnaires distributed to with the disc diffusion method were allowed to thaw and veterinarians, veterinary assistants and veterinary 100 µl of the yolk inoculated into the Premi test superintendents were returned. All 39 respondents ampoules and incubated at 80 C for ten minutes an agreed that there is gross misuse or abuse of veterinary later at 64 C for 3 h as described by the manufacturer drugs. Almost all respondents (97.4%) believed that the The positive samples from the test kit were tested for abuse of veterinary drugs is common in intensive tetracycline residues. A modified commercial test kit management. All respondents believed that veterinary (Premi®Test) protocol was carried out according to drug misuse or abuse could result in the presence of Stead et al. (2007). The modification is the addition of a residues in animal tissues or their products. Most Tetracycline (TCN) buffer to the samples. The TCN buffer respondents (92.3%) believed that the slaughter of was prepared using 7.88 g TRIS-HCL at 50 mM, 2.19 g animals during treatment is common and could lead to the occurrence of drug residues. 25.6% of the Int. J. Poult. Sci., 9 (10): 959-962, 2010 respondents believed that meat or eggs from birds such as in eggs, which may give a false positive result undergoing treatment with veterinary drugs could be with the disc method. In addition, the kit can be used in consumed, 20.5% believed that such meat or eggs samples such as eggs where higher temperature may could be sold to the public and 90% believed that such cause the egg to cake thereby preventing the disc to meat should be condemned. On the familiarity of soak and absorb any antimicrobial agent that may be respondents to local, national and international laws on present. Determining the antimicrobial agents present drugs use, 76.9% said they were familiar with laws.
in the sample is difficult with both the Premi®Test kit andthe disc method. Both methods can not determine the DISCUSSION
quantity of the antimicrobial agent present in the sample Antimicrobial use for bacterial and viral diseases is except when combined with other tests. However, the common in Nigeria (Kabir et al., 2004). The disease use of these simple secondary screening assays status of an animal and the way in which drugs are provided an insight into the level of abuse of veterinary administered influence the potential for residues drugs in the poultry industry in Nigeria and allows a (Kaneene and Miller, 1997). Disease condition may suspect positive sample to be reliably directed to the affect the pharmacokinetics of the drug, its metabolism appropriate chemical method for confirmatory analysis.
or the presence of infection and/or inflammation, whichmay cause the drug to accumulate in affected tissues Conclusion: In order to minimize the occurrence of drug
(Kaneene and Miller, 1997). This study showed that residues in poultry and poultry products in Nigeria, 33.3% of farms were either not adhering to measures need to be taken. These include regulating recommendations on drug use or were unintentionally the sales of veterinary drugs, restricting the manufacture allowing the occurrence of drug residues. This does not and marketing of medicated poultry feed, encouraging come as a surprise because there has not been any farmers to form cooperatives in order to access bank monitoring programme put in place by government loans and to insure their farms. The enforcement of laws neither has there been a deliberate effort to sensitize the for every farm with up to 200 birds to register with the populace on the dangers associated with residues in state veterinary services and public education on the animal products (Kabir et al., 1999). Many farmers do not hazards of residues in animals are also required.
insure their farms and thus the occurrence of diseasecreates large financial losses. This may be the reason ACKNOWLEDGEMENTS
why farmers rarely observe withdrawal periods We wish to acknowledge the assistance and contributions of the following staff of the Bacterial The age of farmers, their experience, level of education Research Division, NVRI, Vom; Dr. M.O. Odugbo, Dr. P.A.
and the frequency of administration of veterinary drugs Okewole, Mr. S.S. Ardzard, Mrs. L.A. Okeke, Mrs. O.T.
had no significant difference with the occurrence of Ajayi, Mr. G. Gullek and Mrs. F. Choji for the success of residues in poultry. As the flock size increased, the tendency of antimicrobial residue on the farm alsoincreased because large farms were more likely to take REFERENCES
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