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zoom RSS 食肉生産での抗生物質使用の制限を/多剤耐性菌 米国医療事情

<<   作成日時 : 2010/09/16 20:10   >>

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 離乳後の感染しやすい時期に数週間にわたりブタに抗生物質を投与し、さらにその後数ヶ月は少ない餌でも発育が促進するように抗生物質を投与する。現在の米国の大規模な集中農場では、健康な動物に抗生物質を投与することが普通に行われている。
 しかしこのことが、耐性サルモネラ菌や毎年数百万人の危険な薬剤耐性大腸菌などによる膀胱感染症を引き起こしたりといった、現代医療の増大する困難に影響を及ぼしている。
 数十年に及ぶ議論の後、FDAは人の健康への明確なリスクを減らす目的で、動物への抗生物質投与にたいするより強固な指針を出そうとしている。家畜生産業者は農場と人の疾患との直接的な関係が証明されていないと主張しているが、米国医師会や米国感染症学会など多数の科学者グループは、健康な動物への抗生物質の使用に強硬に反対している。
 制限の提案者は、EUで2006年にほとんどの非治療用途の抗生物質の使用を禁止したが、結果的にコストの増加なしに対応できていると主張している。
 家畜と鳥肉は、サルモネラ・カンピロバクターなどの薬剤耐性菌による人の腸管感染症や重症な膀胱・血液などの感染を起こす大腸菌感染の原因となっている(最近発生した卵のサルモネラ菌汚染は耐性菌ではなかった)。
 薬物耐性大腸菌菌株の遺伝学研究により、患者から培養されたものと、食品売り場の鳥肉と牛肉から見つかったものが同一であったり、農場から耐性菌株が見つかることがわかっている。
 病院で尿路感染から見つかる最近の最高30%が耐性菌になっている。耐性大腸菌は重症の血液・中枢神経感染にも関連している。人で見つかる耐性大腸菌はほとんどは食物動物由来であるとミネソタ大の感染症専門家ジョンソン博士はいう。
 抗生剤の使用でブタ1頭あたりの餌代を1-3ドル節約でき、最終的に1頭あたり7-10ドル利益が増すと、農場経営者は言う。
 アイオワ州立大のマッキーン博士の試算では、抗生物質の非治療用途への禁止により豚肉のコストを1ポンドあたり5セント上げるだろうという。
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抗生物質の使用と薬剤耐性菌の発生について −家畜用の抗生物質の見直し−
農林水産省消費・安全局

http://www.maff.go.jp/syoku_anzen/20031110/giji.pdf
動物への抗生物質使用を制限/FDA
http://kurie.at.webry.info/201007/article_4.html
新たな多剤耐性「超細菌」による感染が3州で見つかる/米国医療事情
http://kurie.at.webry.info/201009/article_10.html
病院コンピューター入力機器の多剤耐性菌汚染/キーボード・マウス MRSA 緑膿菌 アシネトバクター
http://kurie.at.webry.info/201009/article_9.html
病院内携帯電話による多剤耐性アシネトバクター汚染/医療用PHS 多剤耐性菌
http://kurie.at.webry.info/201009/article_8.html
新たな超薬剤耐性菌の広がり NDM-1
http://kurie.at.webry.info/201009/article_4.html
駆血帯による院内感染の危険
http://kurie.at.webry.info/200708/article_22.html
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U.S. Meat Farmers Brace for Limits on Antibiotics
Brian C. Frank for The New York Times
By ERIK ECKHOLM
Published: September 14, 2010
http://www.nytimes.com/2010/09/15/us/15farm.html


画像At Elite Pork, a large pork farm in Ralson, Iowa, pigs are fed antibiotics for weeks after weaning to ward off possible illness.
RALSTON, Iowa ― Piglets hop, scurry and squeal their way to the far corner of the pen, eyeing an approaching human. “It shows that they’re healthy animals,” Craig Rowles, the owner of a large pork farm here, said with pride.

The questions over antibiotics come at a time when animal confinement methods and other aspects of so-called factory farming are also under attack.

Mr. Rowles says he keeps his pigs fit by feeding them antibiotics for weeks after weaning, to ward off possible illness in that vulnerable period. And for months after that, he administers an antibiotic that promotes faster growth with less feed.

Dispensing antibiotics to healthy animals is routine on the large, concentrated farms that now dominate American agriculture. But the practice is increasingly condemned by medical experts who say it contributes to a growing scourge of modern medicine: the emergence of antibiotic-resistant bacteria, including dangerous E. coli strains that account for millions of bladder infections each year, as well as resistant types of salmonella and other microbes.

Now, after decades of debate, the Food and Drug Administration appears poised to issue its strongest guidelines on animal antibiotics yet, intended to reduce what it calls a clear risk to human health. They would end farm uses of the drugs simply to promote faster animal growth and call for tighter oversight by veterinarians.

The agency’s final version is expected within months, and comes at a time when animal confinement methods, safety monitoring and other aspects of so-called factory farming are also under sharp attack. The federal proposal has struck a nerve among major livestock producers, who argue that a direct link between farms and human illness has not been proved. The producers are vigorously opposing it even as many medical and health experts call it too timid.

Scores of scientific groups, including the American Medical Association and the Infectious Diseases Society of America, are calling for even stronger action that would bar most uses of key antibiotics in healthy animals, including use for disease prevention, as with Mr. Rowles’s piglets. Such a bill is gaining traction in Congress.

“Is producing the cheapest food in the world our only goal?” asked Dr. Gail R. Hansen, a veterinarian and senior officer of the Pew Charitable Trusts, which has campaigned for new limits on farm antibiotics. “Those who say there is no evidence of risk are discounting 40 years of science. To wait until there’s nothing we can do about it doesn’t seem like the wisest course.”

With the backing of some leading veterinary scientists, farmers assert that the risks are remote and are outweighed by improved animal health and lower food costs. “There is no conclusive scientific evidence that antibiotics used in food animals have a significant impact on the effectiveness of antibiotics in people,” the National Pork Producers Council said.

But leading medical experts say the threat is real and growing. Proponents of strong controls note that the European Union barred most nontreatment uses of antibiotics in 2006 and that farmers there have adapted without major costs. Following a similar path in the United States, they argue, would have barely perceptible effects on consumer prices.

Resistance can evolve whenever drugs are used against bacteria or other microbes because substrains that are less susceptible to the treatment will survive and multiply.

Drug use in humans, including overuse and misapplication, clearly accounts for a large share of the surge in antibiotic resistant infections, a huge problem in hospitals in particular. Yet biologists and infectious disease specialists say there is also enormous circumstantial and genetic evidence that antibiotics in farming are adding to the threat.

Livestock and poultry have been identified as the most likely sources of drug-resistant strains of microbes like salmonella and campylobacter that have caused outbreaks of severe intestinal illness in people and of E. coli strains that cause serious bladder, blood and other infections. (Resistant strains have not been implicated in the recent outbreak of salmonella contamination in eggs.)

In a letter to Congress in July, Dr. Thomas R. Frieden, director of the Centers for Disease Control and Prevention, cited “compelling evidence” of a “clear link between antibiotic use in animals and antibiotic resistance in humans.”

As drug-resistant strains of microbes evolve on the farms, they are passed along in meat sold in grocery stores. They can infect people as they handle the uncooked product or when eating, if cooking is not thorough. The dangerous strains can also enter the environment via manure or the clothes of farm workers.

Genetic studies of drug-resistant E. coli strains found on poultry and beef in grocery stores and strains in sick patients have found them to be virtually identical, and further evidence also indicated that the resistant microbes evolved on farms and were transferred to consumers, said Dr. James R. Johnson, an infectious-disease expert at the University of Minnesota. Hospitals now find that up to 30 percent of urinary infections do not respond to the front-line treatments, ciprofloxacin and the drug known as Bactrim or Septra, and that resistance to key newer antibiotics is also emerging. E. coli is also implicated in serious blood, brain and other infections.

“For those of us in the public health community, the evidence is unambiguously clear,” Dr. Johnson said. “Most of the E. coli resistance in humans can be traced to food-animal sources.”

The proposed Food and Drug Administration guidelines focus on the use of antibiotics to speed growth. Just how antibiotics have this effect, which has been known for decades, is unclear, but scientists suspect that the drugs improve the absorption of nutrients as they prevent low-grade disease.

Mr. Rowles, the proprietor of Elite Pork and a trained veterinarian himself, estimates that by feeding his pigs an antibiotic in their final months he is saving $1 to $3 per animal in feed costs. For the consumer, this is negligible, but from his perspective it looms larger because, he said, in good years his net profit is only $7 to $10 per animal.

More contentious is the routine use of antibiotics to prevent disease, as Mr. Rowles and other pork producers do with newly weaned pigs.

Dr. James McKean, an extension veterinarian at Iowa State University, said experience in Denmark, Europe’s leading pork producer, showed that ending the practice would result in more illness, suffering and death among pigs, and cause a jump in antibiotic treatments of actual disease.

Dr. McKean estimated that a ban on most nontreatment uses of antibiotics would raise the cost of pork by 5 cents a pound.

Others counter that farmers in Denmark have learned to hold down illness in young pigs by extending the weaning period, altering feeds and providing more space and veterinary scrutiny of the animals. Some of the drugs used in prevention by farmers like Mr. Rowles would also be permitted under the measure before Congress because they are not used in human medicine.

“In the end, the producers will do what is right,” Mr. Rowles said. “We will make sure we deliver a product that meets the needs of consumers.”

“My only concern is that we make decisions in a scientific fashion, not a political fashion,” he said.

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食肉生産での抗生物質使用の制限を/多剤耐性菌 米国医療事情 医師の一分/BIGLOBEウェブリブログ
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