即便在覺(jué)得自己是獨(dú)自一人時(shí)，大家仍會(huì)有許多“伙伴”。實(shí)際上，在人攜帶的細(xì)胞中，只有大約一半屬于人，剩下的都是微生物，比如細(xì)菌、真菌、原生動(dòng)物和病毒。它們?cè)谌说捏w表或體內(nèi)，這聽(tīng)起來(lái)似乎不利于健康，但大多數(shù)微生物對(duì)人都無(wú)害或者有益。許多研究者都認(rèn)為，如果過(guò)度熱衷于殺死“壞”微生物，一些不為人們所知的有益微生物也會(huì)被我們清除掉，從而破壞微生物群的多樣性，它們統(tǒng)稱為人體微生物菌群。有一種理論認(rèn)為，這種現(xiàn)象是糖尿病、多發(fā)性硬化癥和狼瘡等免疫疾病最近在工業(yè)化國(guó)家抬頭的部分原因。該理論引發(fā)了一系列新的研究，比如改善和這些“伙伴”的關(guān)系能否讓這些疾病的發(fā)病率由升轉(zhuǎn)降，再比如能否利用其中的一些微生物來(lái)提高人們的健康水平。

當(dāng)前情況

科學(xué)發(fā)現(xiàn)迅速地把人體微生物和艾滋、肝炎等傳染病、心臟病和癌癥等非傳染病乃至于孤獨(dú)癥、抑郁癥等心理疾病聯(lián)系在一起。這些發(fā)現(xiàn)讓制藥公司和學(xué)術(shù)實(shí)驗(yàn)室猛然出現(xiàn)了眾多尋找可能治療方法的研究，其思路通常是改變腸道微生物——約99%的人體微生物都生活在這里。一些最有希望的研究涉及糞菌移植，移植手段則包括結(jié)腸鏡、內(nèi)鏡和灌腸劑灌入他人糞便。在初步人體臨床試驗(yàn)中，糞菌移植展現(xiàn)出了潛力，可能成為治療艱難梭菌感染復(fù)發(fā)的出色手段。醫(yī)院經(jīng)常出現(xiàn)這種病原體感染，而且美國(guó)每年約有3萬(wàn)人因此喪生。肥胖癥一直是人們談?wù)摰牧硪粋€(gè)充滿吸引力的目標(biāo)。在試驗(yàn)中，接受瘦老鼠糞菌的胖老鼠體重會(huì)變輕，反之亦然。

背景介紹

參與人體微生物項(xiàng)目（Human Microbiome Project）的研究者已經(jīng)記錄了1萬(wàn)多種人身上的微生物。這是一個(gè)國(guó)際性項(xiàng)目，由美國(guó)國(guó)立衛(wèi)生研究院（U.S. National Institutes of Health）牽頭。人的腸道內(nèi)平均有大約38萬(wàn)億個(gè)微生物，重量約0.2公斤。和欠發(fā)達(dá)國(guó)家的居民相比，工業(yè)化國(guó)家居民所攜帶微生物的多樣性要低得多，人們認(rèn)為首要原因是抗生素在醫(yī)藥和農(nóng)業(yè)兩個(gè)領(lǐng)域中的廣泛使用。其他原因還包括自然分娩率和母乳喂養(yǎng)率較低——自然分娩和母乳喂養(yǎng)可將母親的微生物傳遞給孩子，這也許能解釋為什么剖腹產(chǎn)嬰兒的哮喘和過(guò)敏發(fā)病率較高。只喝配方奶粉的嬰兒患肥胖癥和糖尿病的風(fēng)險(xiǎn)較高。社交、戶外活動(dòng)以及和動(dòng)物的接觸較少可能也會(huì)減少這些微生物的數(shù)量。多年來(lái)，科學(xué)家一直都知道和寵物犬一起長(zhǎng)大會(huì)降低兒童患哮喘的可能性——一項(xiàng)研究稱降幅可達(dá)13%，而且主要理由就是微生物多樣性。看來(lái)?yè)崦?ài)犬以及被它舔舐可以讓家庭成員進(jìn)行微生物交換。

存在爭(zhēng)議

研究者強(qiáng)調(diào)，開(kāi)發(fā)基于微生物科學(xué)的治療手段需要時(shí)間。同時(shí)，科學(xué)家們普遍認(rèn)為，“放過(guò)”人體微生物對(duì)工業(yè)化國(guó)家的居民也許有好處。過(guò)度使用抗生素已被斥為增強(qiáng)細(xì)菌耐藥性進(jìn)而創(chuàng)造出超級(jí)細(xì)菌的原因，現(xiàn)在人們懷疑這樣做會(huì)同時(shí)殺死人體腸道內(nèi)的“好”細(xì)菌和“壞”細(xì)菌。醫(yī)生們表示，他們經(jīng)常為感染了病毒的患者開(kāi)不必要的抗生素，原因是患者希望如此，而且也沒(méi)有時(shí)間向他們解釋可以殺死細(xì)菌的藥對(duì)病毒毫無(wú)作用。美國(guó)開(kāi)展了一項(xiàng)旨在減少病患要求的公開(kāi)信息運(yùn)動(dòng)，醫(yī)生開(kāi)的抗生素?cái)?shù)量隨之下降。美國(guó)農(nóng)民大量使用抗生素為牲畜治病防病。歐盟大多數(shù)國(guó)家的抗生素使用量則要低得多，歐盟已從2006年開(kāi)始禁止對(duì)健康牲畜使用抗生素。改善微生物平衡的另一種可能途徑是攝取名叫益生菌的“好”微生物。它們存在于酸奶、味噌、大豆飲料和膳食補(bǔ)充品中。一些研究者看到了益生菌的潛力，但他們的意見(jiàn)需要進(jìn)一步檢驗(yàn)，而且就攝取益生菌來(lái)滿足各種需求而言，攝取多少以及攝取哪種益生菌都沒(méi)有成熟的方案。（財(cái)富中文網(wǎng)）

譯者：Charlie

審校：夏林

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Even when you think you’re alone, you’ve got a lot of company. Of the cells you carry around, only about half, it turns out, are human. The rest belong to micro-organisms — bacteria, fungi, protozoans and viruses — that are on and inside you. That may sound unsanitary, but most of them are either harmless or beneficial. Many researchers think that in our overzealousness to kill bad germs, we’ve knocked off some underappreciated good ones, depleting the diversity of our microbiota, whose collective genes are known as the human microbiome. According to one theory, this has contributed to the recent increase, in industrialized countries, of autoimmune diseases such as diabetes, multiple sclerosis and lupus. That’s led to a spate of new research on whether a better relationship with our fellow travelers could undo that rise, and whether some of our microbes could be deployed to make us even healthier.

The Situation

Scientific findings have come quickly, connecting human microbiota to infectious diseases such as HIV and hepatitis, non-communicable ones like heart disease and cancer, and even psychiatric disorders such as autism and depression. The discoveries have sparked an explosion of research by drug companies and academic labs into possible treatments and cures. The idea, usually, is to alter organisms in the gut, where about 99 percent of human microbiota live. Some of the most promising research involves fecal transplantation — the introduction through colonoscopy, endoscopy or enema of a donor stool. In early human trials, it’s shown potential as a superior treatment for recurrent infection with C. difficile, a pathogen often contracted in hospitals that causes diarrhea and kills about 30,000 people a year in the U.S. Obesity has been discussed as another tantalizing target. In experiments, fat mice transplanted with microbes from thin mice lost weight and vice versa.

The Background

Researchers connected to the Human Microbiome Project, an international effort led by the U.S. National Institutes of Health, have catalogued more than 10,000 microbial species among our companion germs. The average human gut contains about 38 trillion microbes, weighing about 0.2 kilograms (0.4 pounds). Compared with people in less-developed countries, those in industrialized states have significantly less diversity in the microorganisms that populate their bodies. An excessive use of antibiotics, both in medicine and agriculture, is thought to be a leading cause. Lower rates of natural childbirth and breast feeding are others: Those practices pass microbes from mother to child, perhaps explaining why cesarean section babies have higher rates of asthma and allergies, and formula-fed babies are at an elevated risk of obesity and diabetes. Less socializing, outdoor activity and exposure to animals may also deplete microbiota. Scientists for years have known that growing up with a dog lowers a child’s chance of having asthma — by 13 percent, according to one study — and microbial diversity has become the leading explanation. Family members, it seems, swap microbes by petting their dogs and being licked by them.

The Argument

Researchers stress that therapies based on microbiome science will take time to develop. Meanwhile, there’s widespread agreement among scientists that people in industrialized countries would do themselves a favor by going easy on antibiotics. Already blamed for breeding resistance in bacteria and thus creating superbugs, antibiotic overuse is now a suspect in killing off good as well as bad bacteria in the human gut. Physicians say they often prescribe unnecessary antibiotics for viral infections because their patients expect it and there’s no time to explain that a bacteria killer won’t destroy a virus. A public-information campaign in the U.S. aimed at reducing patient demand has corresponded with a decline in antibiotic prescriptions. U.S. farmers use antibiotics intensively on livestock both to treat and prevent disease. Usage is much lower in most countries in the European Union, which has banned dosing healthy animals since 2006. Another possibility for encouraging a better microbial balance is to take in “good” microbes, called probiotics. They can be found in food such as yogurt, miso and soy beverages or in dietary supplements. Some researchers see potential in probiotics, but the case for them requires more investigation, and there are no established protocols for how much or what strains to consume for various purposes.