2019年经济学人 肠道、大脑和孤独症(2)（在线收听）

MTT is a prolonged version of a process already used to treat infection by a bug called Clostridium difficile, which causes life-threatening diarrhoea.

已经有一种被用于治疗艰难梭菌感染（会引起致命的腹泻）的方法，而MTT是这种方法的延伸版。

It involves transplanting carefully prepared doses of faecal bacteria from a healthy individual to a patient.

这种方法包括将精心准备的粪便细菌从健康个体移植到病人体内。

The researchers gave the children, first, an oral antibiotic, a bowel cleanse and an oral antacid

研究人员首先给孩子们口服抗生素、肠道清洁和口服抗酸剂

(to ensure that microbes administered by mouth would survive their passage through the stomach).

（确保口服微生物能在通过胃的过程中能够存活）。

They followed this up with either an oral or a rectal dose of gut bacteria, and then, for seven to eight weeks, a daily antacid-assisted oral dose.

他们对用口服或直肠剂量的肠道细菌进行追踪，然后连续七到八周，每日服用抗酸剂辅助口服剂。

Ten weeks after treatment started the children's Prevotella levels had multiplied 712-fold.

治疗开始10周后，孩子们的普氏菌增加了712倍。

In addition, those of another species, Bifidobacterium, had quadrupled.

此外，另一种双歧杆菌增加了四倍。

Bifidobacterium is what is known as a "probiotic" organism—something that acts as a keystone species in the alimentary ecosystem,

双歧杆菌被称为益生菌生物—它们在食物生态系统中起关键作用，

keeping the mixture of gut bacteria healthy. Now, two years later, although levels of Prevotella have fallen back somewhat,

保持肠道细菌混合物的健康。如今，两年后，虽然普氏菌含量有所回落，

they are still 84 times higher than they were before the experiment started.

但仍比接受试验前高84倍。

Levels of Bifidobacterium, meanwhile, have gone up still further—being five times higher than they had been at the beginning of the study.

同时双歧杆菌的含量仍进一步提升—比研究之初高五倍。

This, says Dr Krajmalnik-Brown, suggests the children's guts have become healthy environments that can recruit beneficial microbes by themselves.

Krajmalnik-Brown表示这意味着孩子们的肠道环境变得健康，可以自己补充有益微生物。

Crucially, these changes in gut bacteria have translated into behavioural changes.

关键是这些肠道细菌的改变转化成了行为的变化。

Even 18 weeks after treatment started the children had begun showing reduced symptoms of autism.

自治疗开始18周后，孩子们孤独症症状开始减弱。

After two years, only three of them still rated as severe, while eight fell below the diagnostic cut-off point for ASD altogether.

两年后，其中仅有三人仍被评定为重度自闭症，8人完全低于ASD的诊断建议值。

These eight thus now count as neurotypical.

因此这8例被定为典型发育。

Exactly how gut bacteria might contribute to autism is a puzzle.

肠道细菌究竟是如何导致自闭症的仍是个谜。

But light has been shed on the matter by the second study,

但第二项研究为这个问题提供了线索，

published this week in Cell by a team led by Sarkis Mazmanian of the California Institute of Technology.

本周加州理工学院Sarkis Mazmanian领导的团队在《细胞》杂志发表了一项研究。

Dr Mazmanian and a group of colleagues that also included Dr Krajmalnik-Brown performed a type of MTT on mice.

Mazmanian博士及其同事（其中也包括Krajmalnik-Brown博士）对老鼠进行了一种MTT。

They collected bacteria from the faeces of both neurotypical and autistic people

他们收集了典型发育和孤独症人群粪便中的细菌

(who ranged in their symptoms from mild to severe) and transplanted these into hundreds of mice.

（他们的症状按轻微到重度排列）并将这些细菌移植到数百只老鼠体内。

They then interbred the recipient mice and studied the offspring of these crosses—

然后他们让受鼠杂交并研究它们的后代—

animals that had picked up the transplanted bacteria from their mothers at birth.

这些动物自出生后便从母亲体内遗传了移植细菌。

Dr Krajmalnik-Brown and Dr Adams are now recruiting volunteers for a large-scale trial of MTT for adults with autism, to see if they, too, can benefit.

目前Krajmalnik-Brown博士和Adams博士正在为MTT大范围成人孤独症试验招募志愿者，他们想知道这种方法是否也有益于成人。

The paradigm, it seems, really is shifting.

范式似乎真的正在转变。