Maryn McKenna finds much to digest in a warning about the demise of our bodily bacteria.
Missing Microbes: How the Overuse of Antibiotics is Fueling Our Modern Plagues
- Martin J. Blaser
Last year, two public-health-agency chiefs chose dramatic language to alert their nations to a menacing health problem — a rise in the spread and severity of bacterial resistance to antibiotics. UK chief medical officer Sally Davies called it a “catastrophic threat”; Thomas Frieden, director of the US Centers for Disease Control and Prevention, spoke of a “nightmare”. They were flagging the emergence of an almost pan-resistant bacterium, carbapenem-resistant Enterobacteriaceae. This is the latest in a series of tough-to-treat organisms — the result of overuse of antibiotics since the 1940s.
In Missing Microbes, Martin Blaser sounds a related alarm. He patiently and thoroughly builds a compelling case that the threat of antibiotic overuse goes far beyond resistant infections. Antibiotics, he warns, are destroying the benign bacteria that are crucial to the functioning of human bodies, and this trend is contributing to health problems from obesity to diabetes and bowel disease.
Antibiotic resistance can be devastating for patients, but it has until recent years received scant attention from policy-makers, as Blaser knows. A physician and microbiologist, he has treated many people with resistant infections. And as past president of the Infectious Diseases Society of America, he pressed the US government to curb antibiotic overuse and encourage drug development.
Blaser, who is also director of New York University's Human Microbiome Project, investigates the personal bacterial ecosystems that allow us to absorb nutrients and develop immunity. He has long studied Helicobacter pylori, a bacterium that thrives in the stomach and can cause ulcers and stomach cancers. Using mouse experiments and epidemiological data, he has shown that H. pylori may also be associated with a reduced incidence of asthma, allergies and severe reflux disease. That should concern us, he writes, because worldwide, the rate of H. pylori infection is going down.
The make-up of human microbiomes is shifting, with diversity declining and keystone species disappearing. Blaser blames these changes on innovations that impede bacterial attempts to set up shop inside us. Examples include germ-killing hand sanitizers, and Caesarean sections that rob newborns of the bacterial kick-start that they usually get by passing through the birth canal. In the United States alone, one-third of all births are now Caesareans.
Blaser is strongest, and most provocative, when he questions a practice that has become routine in much of the industrialized world: feeding small doses of antibiotics to meat animals as growth promoters. The early discovery that antibiotics work as fattening agents gave birth to the entire structure of modern concentrated meat-raising. By saturating the environment with antibiotic residues, Blaser argues, we have effectively recreated that weight-gain programme in humans — and the result has been the seemingly unstoppable increase in obesity, especially in children.
Can the trend of inadvertently destroying our microbiomes be reversed? Blaser is sceptical. The public has been indifferent to warnings about resistance since antibiotic use began: penicillin discoverer Alexander Fleming cautioned in his 1945 Nobel prize acceptance speech that using the drugs carelessly would undermine their power to treat lethal diseases. Antibiotics — like Caesarean sections and hand sanitizers — make modern life easier. Blaser would say that we have ignored Fleming's warning: we have consistently chosen convenient over smart and safe.
The first step, Blaser says, is to roll back antibiotic overuse in agriculture and medicine. After that, he suggests, we should bend our appetite for innovation towards finding ways to repair the microbiome damage that the wonder drugs have done.
Blaser foresees the development of microbial supplements — a more sophisticated version of the faecal transplants already being used in some quarters to combat Clostridium difficile infections — that could restore microbial communities devastated by antibiotics. The regulation of faecal transplants has confounded the US Food and Drug Administration (M. B. Smith et al. Nature 506, 290–291; 2014), but many patients — along with academic researchers in Europe and Australia — have taken to them intuitively and enthusiastically. It seems likely that Blaser's concept of personal, protective microbial cocktails would also find support.
It is urgent that we take these steps soon. Missing Microbes explains that our ancient microbiome is akin to an essential organ; we unthinkingly excised it, and only now are waking up to the implications. Changes to it come with costs, Blaser warns, “but we are only just beginning to recognize them. They will escalate.”
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McKenna, M. Drugs: Gut response. Nature 508, 182–183 (2014). https://doi.org/10.1038/508182a