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5 Drug Residues and Microbial Contamination in Food
Pages 110-141

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From page 110...
... Drug residue control and microbial-contamination surveillance are accomplished through a rigorous, extensive process of sampling, testing, notification, and enforcement. Tens of thousands of samples are collected and processed annually in routine screening procedures aimed at statistically identifying the occurrence of residues and microorganisms.
From page 111...
... FDA also approves drugs used for food-producing animals, establishes tolerance and safe levels for animal drugs and establishes action levels for unavoidable environmental contaminants that might adulterate food. (The section on "Tracking Residues in Food: Regulatory Input" describes tolerance, safe, and action levels.)
From page 112...
... The confirmatory methods are extremely sensitive and validate the presence of exact residue structures and their concentrations as determined by the mass ion of the molecule, using gas or liquid chromatographic separation and isolation procedures followed by mass spectroscopy. Over the years, the action levels of some drug residues have been lowered because of issues related to "sensitivity of the method," which refers to the accuracy and precision of measuring the lowest concentration of a compound.
From page 113...
... For example, for most chemical residues that occur in meat, USDA considers the likelihood of ill effects of one-time or infrequent eating of the meat to be of negligible consequence and risk to the population. TRACKING DRUG RESIDUES IN FOOD Investigators can use sophisticated chemical detection methods or drugs labeled with radioactive markers to study the pharmacokinetics, tissue distribution, and metabolism of a drug or test compound and establish the total residue content of the drug present in the edible tissues and in specific test site tissues of treated animals.
From page 114...
... The tolerance level is established to facilitate monitoring drug residue entry into the food chain and to further aid in regulating the uses of animal drugs. Some producers and drug developers are concerned that this conservative measurement practice is counterproductive to the use of many animal drugs, because the drug concentrations measured in marker tissues are irrelevant.
From page 115...
... NRP collects samples of livestock and poultry tissues at slaughtering establishments under its inspection authority and from import shipments at ports of entry. The samples are analyzed for the presence of unacceptable residue concentrations of animal drugs that might contaminate meat and other tissues.
From page 116...
... Compounds of greatest concern were designated A-1 -- those with a high health hazard potential and high likelihood of residue occurrence. Compounds of least concern were designated D-4 -- those with a negligible health hazard potential and negligible likelihood of residue occurrence.
From page 117...
... A new ranking system is being phased in through 1998 that assesses the health risk through a mathematical function that considers the pharmacokinetic distribution and elimination of drugs in animals, as well as the likelihood of residue consumption, and the inherent toxicological properties of compounds and metabolites. In addition, the evaluation system further refines tolerance levels for different drugs and compounds with regard to slaughter class–compound pairs.
From page 118...
... cFAST = Fast antimicrobial screen test. dSOS = Sulfa-on-site.
From page 119...
... The only official test for detecting drug residues under the Pasteurized Milk Ordinance (PMO) is the Bacillus stearothermophilus disk assay.
From page 120...
... . With the support of NCIMS, FDA initiated the National Drug Residue Milk Monitoring Program (NDRMMP)
From page 121...
... Source: Adapted from National Milk Drug Residue Data Base Fiscal Year 1996 Annual Report; http://vm.cfsan.fda.gov/~ear/milkrp96.html. The Grade A Pasteurized Milk Ordinance The Public Health Service has always held a great interest in dairy products because few foods surpass milk as a single source of dietary elements needed for the maintenance of proper health, particularly in infants and the elderly.
From page 122...
... Similarly, bacteria counts, drug tests, coliform determinations, phosphatase tests, and cooling-temperature checks are performed on pasteurized milk and milk products. For the purpose of this discussion, drugresidue testing of milk and milk products will be the central issue, as drug use in food animals is the major concern of the committee.
From page 123...
... Neither NCIMS nor processors have the authority to test the assays themselves, under their own protocols, or to approve a test kit for use. Appendix N of the PMO deals with drug residue monitoring and farm surveillance.
From page 124...
... The Grade A producer permit can be restored, after the penalty, to a temporary permit if a sample taken from the producer's bulk tank milk is no longer positive for drug residues. In no event may the Grade A permit of the violative producer be reinstated by the regulatory agency unless the responsible producer and a licensed veterinarian have signed a quality-assurance certificate, for display in the milkhouse, which states that the Milk and Dairy Beef Residue Prevention Protocol is in place and is being implemented for the dairy herds from which the adulterated milk, containing violative drug residues, was shipped.
From page 125...
... Unless producers or veterinarians are able to submit a problem at the biennial NCIMS conference and have it addressed, they have little or no input on this important regulatory document. The PMO dictates that drug residue testing should be performed on raw commingled milk at safe and tolerance levels.
From page 126...
... , not to bulk tank or milk from individual animals. Third, neither CVM, private testing companies, AOAC INTERNATIONAL, nor test kit manufacturers have evaluated assay performance under field conditions for appropriate examination of commonly tested milk samples (tanker milk, pasteurized milk, bulk tank milk, individual-animal milk, or milk from single-mammary-gland quarters)
From page 127...
... Other infectious organisms not identified in survey studies that might be present in carrier states in food-producing animals are Leptospira interrogans, Mycobacterium species, Brucella species, Coxiella burnetti, Toxoplasma gondii, Cryptosporidium parvum, and Cysticercus species. The use of antibiotic drugs as prophylactic or therapeutic treatment and the use of probiotics (feeding live beneficial microorganisms to animals to maintain or reintroduce balance in gut ecology; see Chapter 8)
From page 128...
... 128 THE USE OF DRUGS IN FOOD ANIMALS TABLE 5–3 Survey Report of Microbiological Hazards in Swine Mean Percentage of Samples Yielding Pathogenic Bacteria in Swine Fresh Organ Human Pathogen Carcass Meat Meat Salmonella spp. 16.2 14.7 30.0 Campylobacter jejuni/coli 10.0 13.4 -- a Yersinia enterocolitica 3.7 43.7 21.5 Erysipelothrix rhusiopatheae -- 29.5 -- Arcobacter spp.
From page 129...
... DRUG RESIDUES AND MICROBIAL CONTAMINATION IN FOOD 129 Ground Processed Critical Mean Meat Product Source References Prevalence 40.3 35.0 Animal S1–15 24.1 -- -- Animal S16–20 12.8 11.9 38.5 Animal S21–28 27.5 -- -- Animal S29–30 29.5 -- -- Animal S31 89.0 100.0 33.0 Animal S32 66.5 12.0 -- Environment S33–36 29.6 39.0 81.0 Environment S37–39 39.6 -- 1.0 Environment S40–41 1.0 -- 25.5 Environment S42 29.6 -- 5.5 Human S43–46 46.0 -- -- Human S47 1.5 S24 Fukushima 1985 S25 Harmon et al. 1984 S26 Kotula and Sharar 1993 S28 Schiemann 1980 S29 Schiono et al.
From page 130...
... The joint Sentinel Site Study report (arising from the USDA Pathogen Reduction Task Force 1994) of FSIS, CDC, and FDA showed two patterns of disease emergence: low-level, random occurrences and major outbreaks.
From page 131...
... Similarly, the nature of the finished retail product is a considerable factor in the emergence of food-borne disease. The potential for food infection is greater in ground meat and poultry than it is in an intact muscle product like a steak or chop because of the mixing
From page 132...
... For example, children living in India might not be severely affected by some water-borne microorganisms that would be intolerable to visitors from the West. In the animal world, scavengers eat carcasses of dead, diseased animals and appear to suffer no apparent ill effects.
From page 133...
... An outbreak of gastrointestinal disease affecting at least 110 people in England caused by Campylobacter jejuni was associated with drinking inadequately pasteurized milk (Fahye et al.
From page 134...
... 134 THE USE OF DRUGS IN FOOD ANIMALS TABLE 5–6 Survey Report of Microbiological Hazards in Poultry Mean Percentage of Samples Yielding Pathogenic Bacteria in Poultry Fresh Organ Human Pathogen Carcass Meat Meat Salmonella spp. 47.4 41.9 52.7 Campylobacter jejuni 66.2 52.7 63.3 Aeromonas hydrophila 98.0 50.0 100.0 Listeria monocytogenes 22.0 23.8 7.0 Clostridium perfringens 79.0 -- -- Bacillus cereus -- 21.5 -- Staphylococcus aureus -- 40.0 -- Escherichia coli O157:H7 -- 1.5 -- aNot tested.
From page 135...
... DRUG RESIDUES AND MICROBIAL CONTAMINATION IN FOOD 135 Ground Processed Critical Mean Meat Product Source References Prevalence -- a 56.3 Poultry P1–16 46.9 -- -- Poultry P17–32 61.9 -- 6.0 Poultry P33–35 63.5 -- 32.5 Environment P36-48 25.4 -- -- Environment P47 79.0 -- -- Environment P48–49 21.5 -- -- Human P50 40.0 -- -- Human P51 1.5 P27 Gill and Harris 1984 P28 Kinde et al. 1983 P39 Roberts and Murrell 1993 P30 Shanker et al.
From page 136...
... Education, awareness, and observation and diagnosis have certainly assisted in increasing the number of food-borne illnesses reported. Similarly, conclusions on a cause-and-effect relationship between antibiotic use in food animals, on-farm food-animal production practices, and the incidence of disease should not be made quickly or in the absence of definitive, trackable proof and data.
From page 137...
... In contrast, microbial contamination of foods, especially where the contamination is animal-feces-related, is an issue at the time of product harvest, and it has tremendous potential for risk to increase with improper food handling prior to consumption. Practical considerations affect the further propensity for organisms to cause disease, including poorly defined interactions of contaminating bacteria with the environment found in the food product (acidity, salinity, cold-storage effects)
From page 138...
... Within the context of microbial contamination of food, antibiotic-resistant bacteria constitute a subpopulation of organisms that, when present, can be carried within the food product to pose a formidable challenge to treatment and remediation of disease in humans. Based on the number of reported cases, the threat of disease and illness occurring through food contaminated with microorganisms is much greater than the threat of resistance transfer from animals to humans.
From page 139...
... FDA oversees the use of animal drugs. Animal Plant Health Inspection Service oversees ani mal and plant disease.
From page 140...
... • Establish a risk assessment consortium to set priorities for research and data collection, serve as a clearinghouse for data, assess effectiveness of current measures, and recommend modifications and amendments to plans. • Fund the research necessary to establish directives in pathogen avoidance and reduction in food animals, food handling, and storage and cooking, and charge the Office of Science and Technology Policy with coordinating the implementation of these directives in federal programs.
From page 141...
... The high false-positive rate can cause unnecessary dumping of large quantities of milk and it causes unnecessary concern among consumers about the safety of the milk supply. • The committee recommends that resources be identified to support the initiatives of programs that monitor residues and microbial contamination.


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