Agricultural Uses of Antibiotics - ACS Publications - American

12

The

U.S.

Department

of

Agriculture

Meat

and

Poultry

Antibiotic Residue Testing Program

1

2

Bernard Schwab and Jeffrey Brown

Downloaded by UNIV OF CINCINNATI on May 20, 2016 | http://pubs.acs.org Publication Date: September 18, 1986 | doi: 10.1021/bk-1986-0320.ch012

1

U.S. Department of Agriculture, Food Safety and Inspection Service, Beltsville, MD 20705 U.S. Department of Agriculture, Food Safety and Inspection Service, Washington, DC 20250

2

The USA monitoring and surveillance programs for detecting a n t i b i o t i c residues i n the domestic and imported meat supply are described. An overview of the f i e l d / l a b o r a t o r y tests currently i n use i s also provided.

A n t i b i o t i c s are used extensively i n r a i s i n g meat animals and poultry i n the United States (USA) and other nations. The antimicrobials are used as feed additives or medicants; they allow for faster weight gain and more concentrated rearing practices, and protect the maturing animals against the various diseases that may occur on the farm. The Food Safety and Inspection Service (FSIS) of the United States Department of Agriculture (USDA) i s responsible for providing meat and poultry products to the consumer that are safe, wholesome, and unadulterated. Before marketing, meat animals and poultry must be properly withdrawn from a n t i b i o t i c s to ensure that the levels of a n t i b i o t i c s i n edible tissues at slaughter are at or below the tolerances established by the Food and Drug Administration (FDA). FDA i s responsible for the approval and regulation of animal drugs used i n animal husbandry i n the USA. The FDA i s also responsible for establishing tolerances for any a n t i b i o t i c s that may adulterate food products and animal feed. National Residue Program Since 1967 FSIS has conducted the National Residue Program to help prevent the marketing of animals and poultry containing i l l e g a l residues of a n t i b i o t i c s , drugs, and other chemicals. The National Residue Program operates i n three basic modes: monitoring, s u r v e i l l a n c e , and exploratory. Monitoring i s the random sampling of healthy-appearing animals at slaughter. The data gained from analysis of these samples are This chapter not subject to U.S. copyright. Published 1986, American Chemical Society

Moats; Agricultural Uses of Antibiotics ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

AGRICULTURAL USES OF ANTIBIOTICS


138

used to define the p r o f i l e or residues over time and to i d e n t i f y problems• Surveillance i s biased sampling directed at p a r t i c u l a r carcasses or products. Surveillance comes into play when the Program receives information from monitoring or other sources, e.g., from slaughter inspection, indicating that adulterating residues may be present. Product may be held u n t i l laboratory tests determine the appropriate regulatory action. Exploratory sampling i s done generally to gain information about possible residues of concern. A l l exploratory projects have i n common the negative c h a r a c t e r i s t i c that t h e i r design i s not suitable f o r immediate regulatory action. However important to the Program, they are b a s i c a l l y f o r informational purposes. Meat and Poultry products exported to the USA are also checked f o r a n t i b i o t i c residues. Imported meat must meet the same residue standards as those established for domestic production. Monitoring, s u r v e i l l a n c e , and exploratory subprograms as defined above are carried out on foreign production marketed i n the USA. Compound Evaluation and Selection It i s , of course, not f e a s i b l e to monitor residues of a l l chemicals that t h e o r e t i c a l l y could contaminate meat and poultry, nor i s t h i s necessary to adequately protect public health. It i s important, however, to monitor those chemicals that are most l i k e l y to present the greatest r i s k . FSIS i s currently implementing a new prototype system f o r more refined categorization of residues as to their potential impact on public health. FSIS believes that this Compound Evaluation System (CES) w i l l be s u f f i c i e n t l y f l e x i b l e to permit rapid response to new information that may affect previous rankings and to allow f o r the use of s c i e n t i f i c or expert judgement. As such, the CES should serve as a useful guide i n the planning and a l l o c a t i o n of FSIS program resources f o r those residues considered to have the greatest potential effect on public health. Methods and Testing Program The e f f o r t to reduce the incidence of a n t i b i o t i c residues i n the meat supply involves not only FSIS and FDA, but also the farmers, t h e i r trade associations, feed manufacturers, and veterinarians. FSIS has expended considerable resources recently investigating several a n t i b i o t i c residue problems, such as sulfonamides and a n t i b i o t i c residues i n bob veal calves, and sulfonamides and chloramphenicol i n pigs. Agency representatives apprise the industry and other involved parties of the problem and provide resources such as educational materials, f i e l d t e s t s , and other assistance to resolve the residue problems on the farm before the animals are sent to market. When these e f f o r t s do not produce the desired r e s u l t s , the Agency implements intensive in-plant testing programs to detect the residues i n the meat at slaughter and takes corresponding regulatory action against the offending producers.


12.

SCHWAB AND BROWN

USDA Antibiotic Residue Testing Program

139

Tests f o r A n t i b i o t i c Residues FSIS currently uses a variety of tests for detecting a n t i b i o t i c residues i n meat; among these are f i e l d , in-plant, and laboratory screen tests, bioassays, immunoassays, and related biochemical techniques.


F i e l d , In-Plant, and Laboratory

Tests

FSIS has developed a series of overnight, inexpensive, easy to perform swab bioassay tests f o r screening tissues, body f l u i d s , or feed extracts f o r a n t i b i o t i c residues. The swab tests are used on the farm, i n the slaughter plant, or i n the laboratory for t h e i r designated purpose. Swab test results indicate whether antimicrobial a c t i v i t y i s present i n the sample at or above allowable levels or absent. Further testing with more sophisticated tests i s required to i d e n t i f y and quantify the a n t i b i o t i c s producing the antimicrobial a c t i v i t y . These are usually done i n a laboratory as required. B a s i c a l l y , a l l swab tests are performed i n the same manner. The analyst (farmer, v e t e r i n a r i a n , laboratory s c i e n t i s t , or any other user) saturates a cotton tipped swab with sample tissue f l u i d s , serum, urine, or feed extract. He then firmly places the saturated cotton swab on the surface of the appropriate growth medium previously surface streaked with the working d i l u t i o n of the appropriate susceptible test organism. The test i s then incubated at the proper temperature overnight and observed the next day for antimicrobial a c t i v i t y . If there i s a zone of i n h i b i t i o n (no growth of the test organism) around the sample swab, the test i s p o s i t i v e ; no i n h i b i t i o n indicates that antimicrobials are absent or below detectable levels i n the sample tested. There are currently five swab tests i n use: o o o o o

Live Animal Swab Test (LAST) Residue Avoidance Feed Test (RAFT) Swab Test on Premises (STOP) Calve Antibiotic/Sulfonamide Test (CAST) STOP I I

LAST i s used by farmers, veterinarians, and other interested parties to screen urine from c u l l dairy cows for a n t i b i o t i c residues before marketing. I f the LAST test i s p o s i t i v e , the animal i s retained for several days and retested before s a l e . A negative LAST test allows the farmer to market h i s c u l l cow with a high degree of confidence that the edible meat, l i v e r , kidney, e t c . , at slaughter w i l l be a n t i b i o t i c residue free or below established tolerances. RAFT allows feed m i l l operators, farmers, e t c . , to test feed or feed constituents f o r antimicrobial a c t i v i t y . A feed containing an a n t i b i o t i c added i n t e n t i o n a l l y (medicated feed) or unintentionally (contaminated feed) and detectable by RAFT w i l l result i n a p o s i t i v e RAFT t e s t . STOP i s used by Federal Meat inspection personnel in-plant to check tissues from slaughtered animals for a n t i b i o t i c residues.



140

AGRICULTURAL USES OF ANTIBIOTICS

Edible tissues from STOP-positive animals are retained u n t i l tested further by FSIS laboratories. If the laboratory report indicates a n t i b i o t i c at or above tolerance l e v e l s , the v i s c e r a and/or the carcass are condemned. If a n t i b i o t i c levels are below tolerance levels upon laboratory t e s t i n g , the tissues are released into the food supply. In-plant STOP-negative animals are released without delay into the food chain. STOP may be used to test a l l food animals and poultry f o r a n t i b i o t i c residues. Since STOP began i n 1979, the incidence of a n t i b i o t i c residues i n the bovine meat supply has been reduced to approximately one percent. CAST allows FSIS meat inspectors to test young veal calves at slaughter for a n t i b i o t i c and sulfonamide residues. This category of veal animal has a lengthy past history of a n t i b i o t i c misuse at slaughter. A positive CAST finding r e s u l t s i n the animal's condemnation or requires further testing at an FSIS laboratory. A CAST-negative animal i s released into the food chain without delay. The FSIS CAST program, started i n June 1985, has been successful i n reducing the incidence of a n t i b i o t i c s and sulfonamides i n the veal supply. STOP II currently i s used exclusively by FSIS laboratories to screen import and domestic monitoring samples for t y l o s i n , novobiocin, virginiamycin, and lincomycin. This test detects these compounds at or above established tolerance l e v e l s . Positive findings indicate that these drugs may be present and were not properly withdrawn before the animals was sold for slaughter. Other tests used by FSIS to detect, i d e n t i f y , and/or quantify a n t i b i o t i c residues i n meat are primarily designed for laboratory use. The conventional bioassays based on methodology developed by FDA and expanded by FSIS use four extractant buffers, five test organisms, five growth media, two incubation temperatures, and p e n i c i l l i n a s e to detect, i d e n t i f y , and/or quantify a n t i b i o t i c s such as the p e n i c i l l i n s , streptomycins, t e t r a c y c l i n e s , neomycins, erythromycin, t y l o s i n , e t c . Bioassay laboratory r e s u l t s are used by FSIS to take regulatory action and by FDA to prosecute farmers with h i s t o r i e s of improperly withdrawing a n t i b i o t i c s before marketing t h e i r herds or f l o c k s . Certain drugs such as chloramphenicol require additional tests f o r t h e i r detection and q u a n t i f i c a t i o n i n meat t i s s u e s . The Competitive Enzyme Labeled Immunoassay for Chloramphenicol (CELIA) was developed and i s used by FSIS laboratories to detect and quantify this drug i n the meat supply; chloramphenicol i s not approved for use i n food animals. CELIA detects 5 ppb chloramphenicol i n tissue extracts. The a n t i b i o t i c i d e n t i f i c a t i o n c a p a b i l i t i e s of FSIS laboratories have rapidly expanded during the past year. Commercially-produced ELISA-type immunoassays, such as the E-Z Screen, are being rapidly adapted by FSIS laboratories for use i n testing meat extracts and body f l u i d s for various a n t i b i o t i c s . These tests are r e l a t i v e l y inexpensive, s p e c i f i c , sensitive to appropriate l e v e l s , and provide results on the same day. Within the next several years, FSIS laboratories w i l l be able to screen f o r and confirm the presence of at least 22 d i f f e r e n t a n t i b i o t i c s .



12.

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BROWN

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Biochemical sophisticated separation techniques are also used when necessary to confirm and quantify immunoassay test r e s u l t s . FSIS laboratories also use chemical techniques and instrumentation to i d e n t i f y select a n t i b i o t i c residues. The tetracyclines of interest are i d e n t i f i e d by t h i n layer chromatography. Sulfonamides are detected and quantified by fluorescence t h i n lay chromatography and confirmed by gas chromatography/mass spectrometry. Amoxicillin and gentamycin are i d e n t i f i e d and/or quantified by high pressure l i q u i d chromatography. Similar techniques are used to i d e n t i f y ionophores and other antimicrobials of i n t e r e s t . In conclusion, FSIS i s making a determined e f f o r t to reduce a n t i b i o t i c and other man-incurred residues i n the meat supply. The Agency i s providing resources such as educational materials and inexpensive screen tests to industry for preventing antimicrobial residues i n meat animals and poultry before marketing. Screen tests such as STOP and LAST are used in-plant by inspectors to check meat and poultry at slaughter. Additional in-plant screen tests are planned for introduction soon. Laboratory c a p a b i l i t i e s are also being rapidly expanded by improving the bioassays and by introducing rapid, s e n s i t i v e , inexpensive ELISA-type immunoassays. Sophisticated biochemical/physical techniques are also in-place or under active evaluation. R E C E I V E D May

2, 1986


Agricultural Uses of Antibiotics - ACS Publications - American

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