|
Antimicrobials destroy bacteria, viruses, fungi, algae, and other microbes. The cells of bacteria (prokaryotes), such as salmonella, differ from those of higher-level organisms (eukaryotes), such as fish. Antibiotics are chemicals designed to either kill or inhibit the growth of pathogenic bacteria while exploiting the differences between prokaryotes and eukaryotes in order to make them relatively harmless in higher-level organisms. Antibiotics are constructed to act in one of three ways: by disrupting cell membranes of bacteria (rendering them unable to regulate themselves), by impeding DNA or protein synthesis, or by hampering the activity of certain enzymes unique to bacteria.〔(Todor’s Online Textbook of Bacteriology ), Kenneth Todor, PhD., 2008 (last visited Oct 1, 2011)〕 Antibiotics are used in aquaculture to treat diseases caused by bacteria.〔Antibiotic use in aquaculture: development of antibiotic resistance – potential for consumer health risks. Alderman, D.J. and T.S. Hastings. Int. ''J. Food Sci. Technol.'' 33: 139-155. 1998.〕 Sometimes the antibiotics are used to treat diseases, but more commonly antibiotics are used to prevent diseases by treating the water or fish before disease occurs.〔"Ecotoxicity of mixtures of antibiotics use in aquacultures". ''Environ. Toxicol. Chem.'' 25: 2208-2215. Christensen, A.M., Ingersley, F., and Baun, A. 2006.〕 While this prophylactic method of preventing disease is profitable because it prevents loss and allows fish to grow more quickly, there are several downsides. The overuse of antibiotics can create antibiotic-resistant bacteria. Antibiotic-resistant bacteria can spontaneously arise when selective pressure to survive results in changes to the DNA sequence of a bacteria allowing that bacteria to survive antibiotic treatments. Because some of the same antibiotics are used to treat fish that are used to treat human disease, pathogenic bacteria causing human disease can also become resistant to antibiotics as a result of treatment of fish with antibiotics.〔Antimicrobial agents in aquaculture: potential impact on health. APUA Newsletter. 18: 1-6. Angulo, F.J. 2000.〕 For this reason, the overuse of antibiotics in treatment of fish aquaculture (among other agricultural uses) could create public health issues.〔"Public health consequences of use of antimicrobial agents in food animals in the United States". ''Microb. Drug Resist'' 9: 373-379. Anderson, A.D., J.M. Nelson, S. Rossiter and F.J. Angulo. 2003.〕 ==Overview== The issue has two sides. In some foreign countries, clean water supplies for aquaculture are extremely limited.〔(Tainted Seafood Reaching U.S., Food Safety Experts Say ), Nicole Gilbert, News21, 2011 (last visited Oct. 2011).〕 Untreated animal manure and human waste are used as feed in shrimp farms and tilapia farms in China and Thailand, in addition to the collection of waste products accumulating from inadequate sewage treatment.〔 In order to prevent the spread of bacteria and disease in contaminated water, some foreign fish farms put U.S.-banned antibiotics into their fishmeal.〔 However, because the more stringent growing regulations in the US increase the price of food, imports from nations without these regulations are increasing based on price and profit.〔(SEAFOOD SAFETY, FDA Needs to Improve Oversight of Imported Seafood and Better Leverage Limited Resources ), United States Government Accountability Office, April 14, 2011〕 Between 1995 and 2005, the first ten years of the NAFTA-WTO era in the US, seafood imports increased 65 percent and shrimp imports increased 95 percent.〔(TRADE DEFICIT IN FOOD SAFETY, Proposed NAFTA Expansions Replicate Limits On U.S. Food Safety Policy That Are Contributing To Unsafe Food Imports ), Public Citizen’s Global Trade Watch, 2007〕 Today, 80 percent of American seafood is imported, about half coming from aquaculture.〔 China, Thailand and Vietnam together account for 44 percent of seafood imports into the United States.〔China 23%, Thailand 16%, and Vietnam 5%. (SEAFOOD SAFETY, FDA Needs to Improve Oversight of Imported Seafood and Better Leverage Limited Resources ), United States Government Accountability Office, April 14, 2011〕 The FDA has been testing for chemicals in aquaculture products for over two decades. In November 2005, the testing program for aquaculture drugs was revised to include antibiotics such as chloramphenicol, fluoroquinolones, nitrofurans, and quinolones, as well as antimicrobial compounds like malachite green that are not approved for use in aquaculture fish.〔USFDA, Industry Efforts Reduce Use of Unapproved Drugs. Global Aquaculture Advocate. July, August, 2006 Issue. p.38-39. Collette, B.〕 From October 1, 2006, through May 31, 2007, FDA tested samples of catfish, basa, shrimp, dace, and eel from China, finding twenty-five percent of the samples to contain drug residues.〔(Hearing on "Safety of Chinese Imports" ), statement of Murray M. Lumpkin, M.D., Deputy Commissioner for International and Special Program before the Senate Committee on Commerce, Science & Transportation, July 18, 2007〕 FDA has approved five different drugs for use in aquaculture as long as the seafood contains less than a mandated maximum residue limit: florfenicol, sulfamerazine, chorionic gonadotropin, oxytetracycline dihydrate, oxytetracycline hydrochloride, as well as a drug combination of sulfadimethoxine and ormetoprim.〔 FDA has approved two drugs—formalin and hydrogen peroxide—for which it has not set a tolerance.〔 The FDA now enforces regulations in the US requiring testing of certain imported products for antimicrobial agents under Import Alert 16-131.〔FDA Import Alert 16-131, http://www.accessdata.fda.gov/cms_ia/importalert_33.html〕 The Import Alert provides that the use of antimicrobials during the various stages of aquaculture, including malachite green, nitrofurans, fluoroquinolones, and gentian violet, may contribute to an increase of antimicrobial resistance in human pathogens and that prolonged exposure to nitrofurans, malachite green, and gentian violet has been shown to have a carcinogenic affect.〔 In a consumer brochure, the FDA describes the reasoning for enforcement under the import alert: After FDA repeatedly found that farm-raised seafood from China was contaminated, the agency announced on June 28, 2007, a broader import control of all farm-raised catfish, basa, shrimp, dace(related to carp), and eel from China. During targeted sampling, from October 2006 through May 2007, FDA repeatedly found that farm-raised seafood from China was contaminated with antimicrobial agents that are not approved for use in the United States. More specifically, the antimicrobials nitrofuran, malachite green, gentian violet, and fluoroquinolones, were detected.〔How FDA Regulates Seafood, FDA, 2007. (http://www.fda.gov/downloads/ForConsumers/ConsumerUpdates/UCM106813.pdf)〕 Due to limitations on funding and resources, U.S. Government Accountability Office states that only 1% of seafood, compared with 2% of all imports, is inspected and only 0.1% of all seafood is tested for antibiotic residue.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Antimicrobials in aquaculture」の詳細全文を読む スポンサード リンク
|