Clinical journals and the media these days are full of reports describing bacterial strains that are resistant to our most powerful antibiotics. Most of this information has focused on the problem of bacterial resistance, but it is only part of the story. Physician Martin J. Blaser, who directs the Human Microbiome Program at New York University, takes a distinctly different approach. For years, his lab has been studying the effects of antibiotic treatment on mice. This work hints at another, less obvious but potentially just as serious consequence of the unfettered application of antibiotics which is covered in his recent book, Missing Microbes. (1)
As Blaser reports, “The magnitude of antibiotic use is enormous, and it has crept up year after year. In 1945 an article in the
Journal of Clinical Investigation reported on the great efficacy of penicillin in treating sixty-four patients with pneumonia. Such treatment, on that scale, produced almost miraculous results. But by 2020, health-care providers prescribed 258 million courses of antibiotics to people in the United States. This more than a million-fold difference in scale amounts to about 833 prescriptions for every thousand people across the country.”
The highest prescription rate was for children under the age of two: 1,365 courses per 1,000 babies. This means that the average American child received nearly 3 courses of antibiotics in his or her first two years of life. They go on to receive, on average, another 8 courses for the next eight years. Extrapolating form the current Centers for Disease Control and Prevention Statistics, the data suggest that, on average, children receive about 17 courses of antibiotics before they are twenty years old. This is a big number, but it is in line with prior studies in the United States and other developed countries.
Young adults in their twenties and thirties receive, on average, another thirteen courses of antibiotics. This means that our young people are taking thirty courses of these potent drugs before the age of forty. This is the average. Some people take more, some less. But the implications loom large. Many of the young women will be mothers of the next generation who will be providing initial microbiomes to their children.
There is an additional problem and it is not just that of people overusing antibiotics. It stems from how we treat animals on the farm.
Most antibiotics produced in the United States don't go to humans but to those massive feedlots we pass on the freeways for cows, swine, chickens and turkeys. Agricultural science operates to maximize meat production, with a particular focus on optimizing feed efficiency—the conversion of calories in animal feed into meat. Feeding antibiotics to farm animals plays a central role in that process, fattening them up.
Blaser adds, “Today an estimated 70 to 80 percent of all antibiotics sold in the United States are used for the single purpose of fattening up farm animals: hundreds of millions of cattle, chickens, turkeys, pigs, sheep, geese, ducks and goats. In 2011, animal producers bought nearly 30 million pounds of antibiotics, the largest amount ever recorded, for their livestock. We don't know the exact number because these amounts are closely guarded secrets.”
The problem is not limited to the resistant bacteria that come to us in the food we buy from industrial farms. The antibiotics themselves arrive in our food, particularly in meats, milk, cheeses and eggs. The FDA requires farmers to establish a washout period between giving the last dose of an antibiotic and when the animal is slaughtered. But inspections are infrequent and enforcement is minimal. Foods on our supermarket shelves are allowed maximum residue limits for antibiotics, establishing upper boundaries of what is permitted. For example, milk can legally have up to 100 micrograms of tetracycline per kilogram. This means that a child who drinks two cups of milk a day will ingest about 50 micrograms of tetracycline every day. Blaser notes that this is not a lot, but consider the fact that many children drink milk every day, year after year. And that level is just for tetracycline. All other antibiotics have their own allowable limits. A 1990 report indicated that 30 to 80 percent of milk samples had detectable antibiotics, especially sulfa drugs and tetracycline.
Here's the real kicker Blaser drives home! Across the board, the incidence of an array of chronic diseases—many of which used to be passingly rare—is increasing. Over the past 60 years, the rate of juvenile diabetes in developed nations has doubled every 20 years. The number of children with eczema, a chronic skin condition has tripled. Asthma and food allergies are on the rise, as is autism, irritable bowel syndrome, and myriad other diseases. Superficially these diseases appear unrelated, but Blaser daringly suggests that they may all share the same root cause: antibiotics. What was once our salvation form acute diseases may now be our chronic curse.
If Blaser's conclusions seem unusual, it might be because his research focuses on a little known category of experiments examining the effects of antibiotics. Most antibiotics studies focus on the drug's effects on the pathogens they are untended to destroy. Blaser instead turns his attention to the billions of other bacteria that live innocuously, or even beneficially, in and on the human body: the personal microbiome that each of us carries, notes Margaret Clark. (2)
Many antibiotics currently on the market are broad spectrum, meaning that they do not act specifically against the pathogen causing the disease. So what happens to our beneficial bacteria when we take these medicines? Blaser details a variety of mouse experiments performed in his lab suggesting that even a single course of antibiotics may have long term effects on the microbiome, particularly if the dose is consumed early in life.
With mouse experiments, Blaser found a connection between antibiotic treatments and increased incidence of obesity, particularly when antibiotics are given early in life. Further experiments revealed that antibiotic treatment coupled with a high-fat diet led to an even more pronounced increase in body fat. Although such experiments cannot be ethically or practically carried out in humans, Blaser discusses a British survey of children that lends credence to the idea that exposure to antibiotics in youth may led to obesity later in life. (2)
One last item before discussing antibiotics in Europe has to do with recent action in the United States. McDonald's says it plans to require chicken suppliers to stop using antibiotics important to human medicine within two years. The company says it suppliers will still be able to use a type of antibiotic called ionophores that keeps chickens healthy and isn't used in humans. McDonald's also said that late this year it will no longer serve milk from cows treated with a particular artificial growth hormone. (3)
Chipotle and Panera already say they serve chicken raised without antibiotics, but the announcement by McDonald's is notable because of its size: the company has more than 14,000 US locations. Chipotle has nearly 1,800 locations, while Panera has almost 1,900.
What about Europe?
The use of antibiotics in animal production to promote growth has been banned in the EU and therefore in France since 2006. The action plan for the reduction of the risks of antibiotic resistance in veterinary medicine was launched in France on November 18, 2011. It aims to achieve a reduction of 25 % in use of antibiotics in animal health over five years by developing alternatives capable of protecting animal health, while avoiding recourse to antibiotics. (4)
Yet, nine years after the campaign's launch, France is still one of Europe's biggest consumers of antibiotics and trends are moving in the wrong direction. A new report by France's national health has sounded alarm belts over the number of antibiotics being popped by the French—a whopping 30 percent more than the European average. (5)
The European Commission estimates that infections caused by micro-organisms resistant to antimicrobial drugs are responsible for the deaths of 25,000 EU patients each year, and an additional cost of 1.5 billion euros arising from health care and lost productivity due to these phenomena.
Back to Blaser's book. Margaret Clark sums it up well,, “Missing Microbes focuses welcome attention on the possible consequences of disturbing the delicate balance between our bodies and the billions of bacteria that we human host. Blaser gradually and artfully connects antibiotic related disruption of our microbiomes with the proliferation and entrenchment of chronic disease, providing enough background to make the material accessible for readers unfamiliar with the field. Although some of these connections remain speculative, the volume of evidence presented throughout the book is hard to ignore, and the warning comes across strong and clear.”(2)
Jack Dini
Livermore, CA
References
1. Martin J. Blaser, Missing Microbes, (New York, Henry Holt and Company, 2014)
2. Margaret Clark, “Review of Missing Microbes,”
American Scientist, March/April 2015
3. Associated Press, “McDonald's to drop antibiotics, hormones from chicken, milk products,”
fayobserver.com, March 5, 2015
4. “Reduction of risk of antibiotic resistance,”
www.ambafrance-us.org, September 20,2012
5. “How bad is France's addiction to antibiotics?”,
www.thelocal.fr/2014, November 7, 2014
