Missing Microbes: How the Overuse of Antibiotics Is Fueling Our Modern Plagues (37 page)

in the next twenty-one years:
A. Nomura et al., “
Helicobacter pylori
infection and the risk for duodenal and gastric ulceration,”
Annals of Internal Medicine
120 (1994): 977–81.

in the other organisms present and their distribution:
M. J. Blaser, “Helicobacters are indigenous to the human stomach: duodenal ulceration is due to changes in gastric microecology in the modern era,”
Gut
43 (1998): 721–27.

12. TALLER

one of my colleagues at NYU:
Lewis Goldfrank, MD, chair of the Department of Emergency Medicine at NYU Langone Medical Center and at Bellevue Hospital Center.

a rural community in Guatemala:
L. Mata,
The Children of Santa Maria Cauque: a Prospective Field Study of Health and Growth
(Cambridge, MA: MIT Press, 1978).

the development of adult height:
A. S. Beard and M. J. Blaser, “The ecology of height: the effect of microbial transmission on human height,”
Perspectives in Biology and Medicine
45 (2002): 475–98.

acquired in the first few years of life:
Even today, we don’t fully know how
H. pylori
is acquired in early life. We know that having an
H. pylori
–negative mother strongly reduces the risk of a child acquiring the organism, but thus far it has not been found in the vagina, and even in communities in which nearly all of the mothers are positive, we rarely detect it in their children before the age of one year. Either it was there all along and was suppressed or it is actually acquired later, still from the mother or from siblings, father, or friends (in day care and school). Or it is possible that for one hundred positive children, it is a mixture of all of these routes, but it remains a mystery. We know that it is not from the family dog, because dogs don’t carry
H. pylori
; they have their own helicobacters.

the same fecal-oral route:
This is a mechanism for transmitting microbes in the feces of one person into the mouth of another. Food, water, hands may be intermediaries. Infectious diseases such as polio, hepatitis A, and typhoid fever are transmitted this way.

the hormones ghrelin and leptin:
C. U. Nwokolo et al., “Plasma ghrelin following cure of
Helicobacter pylori
,”
Gut
52 (2003): 637–40; and F. François et al., “The effect of
H. pylori
eradication on meal-associated changes in plasma ghrelin and leptin,”
BMC Gastroenterology
11 (2011): 37.

keeping records of it:
Beard and Blaser, “The ecology of height.”

bad things can happen:
M. J. Blaser and D. Kirschner. “The equilibria that allow bacterial persistence in human hosts,”
Nature
449 (2007): 843–49.

13. … AND FATTER

visiting scholars from around the world:
But where did the money come from to do the work? There is a paradox in the way that medical science is funded in the United States and elsewhere. In order to get a grant, you must have “preliminary data” that support the idea to be tested, to see whether it may be feasible. But how do you do the feasibility studies without the money that the grant provides? It is a catch-22. I was fortunate at the time to have the means to fund a new idea. First, because I had a number of ongoing research projects, I had amassed over the years equipment and supplies that we could use for a new project. Then, being at a university, there were students and trainees who were looking for a new project, a way to develop their own career track. Ilseung came my way for that reason. I also had received support from several philanthropists that was not exactly earmarked; I could spend it at my discretion. We often say that discretionary money is worth double because of its flexibility. With that support, I could make a commitment to Laurie when she was looking for a lab in which to do graduate work. Finally, there is luck, too. A colleague told me about a neighbor who was looking to work in the lab for a summer. He also told me that she was a student at Princeton. I felt that was a good predictor that she would have something on the ball, and when I met Yael that premise was immediately confirmed. In the United States, the conduct of science is very entrepreneurial, and after good ideas hard work is the sine qua non of success.

“What’s happening to their body composition?”:
Ilseung later applied for and received an NIH-supported grant from NYU’s Clinical and Translational Science Institute (CTSI) that allowed him to conduct this research. CTSI director Dr. Bruce Cronstein, who was a member of a mentoring committee to help Ilseung solve research problems, has studied the metabolism of bone for many years and had a DEXA machine that he used for his own mouse studies. He made the suggestion that opened up new vistas for us. In science, it also “takes a village” to get things done.

the adipose tissue, where fat is stored:
I. Cho et al., “Antibiotics in early life alter the murine colonic microbiome and adiposity,”
Nature
488 (2012): 621–26. This was Ilseung’s major work in the lab and involved him and twelve other scientists—biochemists, animal experimenters, informaticists, gene expression analysts—each contributing to a different aspect of the work. But Ilseung’s patient studies and the sixteen months we spent conducting new experiments and clarifying our work for the anonymous reviewers and the editors of
Nature
paid off, and the paper was finally published, more than five years after the work had started.

But when they are conventionalized
: The germ-free state is artificial; there are no germ-free animals except within specialized laboratories. When germ-free animals have their microbiota restored, it is said that they have been “conventionalized” back to the usual (natural) state.

from the normal-weight mouse donor:
In Jeff’s experiments, the germ-free mice can be used as living test tubes that can react to the newly introduced microbiota. (“Germ-free” means that the playing field is even and clean, tabula rasa.) (P. Turnbaugh et al., “A core gut microbiome in obese and lean twins,”
Nature
457 [2009]: 480–84.)

can make a big difference:
Laurie later did studies to assess how faithfully we had transferred the microbes from their original hosts to the recipients. The DNA sequencing results showed that we did amazingly well. Even microbes for which we had the evidence of only a single sequence in our snapshot of what was there were well represented in the recipients. Thus we had confidence that the germ-free mice were colonized with what actually was in the STAT or control mice. Interestingly, the community of STAT microbes didn’t do as well in their new hosts as the community of untreated microbes. The population was less resilient, and were less resistant to invasion by new species. In this second generation of STAT mice, the microbiota were punier, and I worry about this. See chapter 15, “Antibiotic Winter.”

all the antibiotics prescribed for American children:
We decided to study the two classes of antibiotics most commonly used for human children. The first, beta-lactams, include penicillin, amoxicillin, Augmentin (amoxicillin with a second compound to inhibit bacterial enzymes that would inactivate it), and cephalosporins. Amoxicillin is the number-one drug prescribed to young children in the United States and in most developed countries. In 2010 there were nearly 23 million courses of amoxicillin or Augmentin prescribed to children in the United States and more than 6.5 million of those courses were for children under the age of two. (G. Chai et al., “Trends of outpatient prescription drug utilization in U.S. children, 2002–2010,”
Pediatrics
130 [2012]: 23–31.) That averages to nearly one course of those amoxicillin-based antibiotics per young child per year. Macrolides are the second class of antibiotics used for young children. The best known is erythromycin, available for more than fifty years, but in the past twenty years, longer-acting and broader-spectrum agents have been used, including clarithromycin and azithromycin (the Z-pak, which has benefited from a marketing strategy as good as any ever employed). In 2010 U.S. children received more than 10 million courses of azithromycin, which has become the most widely prescribed antibiotic in the United States. It was so expensive that anyone who bought it was likely to use it. (It is now off-patent and the price has dropped.) The tylosin that we used is the macrolide that can most easily and inexpensively be used in mice and for which there is an extensive literature that helped us figure out the correct doses.

the drug that most promotes the recent increases in human height:
The increase in human height began before antibiotics were discovered, at least in the Western countries. But these experiments (both STAT and PAT) indicate that antibiotics—and it is not limited to a single type—affect microbiome composition (see below) and can affect early-life bone development. Certainly this could be part of the story and could explain why the recent height increases in China are recapitulating in forty years the increases that took one hundred years in Europe and the United States.

colleagues at Washington University in St. Louis:
We worked closely together with Drs. Erica Sodergren and George Weinstock, who run a major genome-sequencing center at Washington University in St. Louis. Once we received the sequence information from them, Alex Alekseyenko, an NYU faculty member who is an expert in bioinformatics, decoded and deconstructed the data, and then analyzed it.

passed on to them by their mother:
We could not find evidence for the presence of many of the microbes seen in the mothers and in the control mice. Either they had been permanently eliminated or they were still present but in low numbers, below our ability to detect them—in which case, the bacteria that bloomed under the influence of the tylosin regimen were still suppressing them—long after the tylosin was gone. This can happen because they get such an advantage in early life—a “founder effect”—that they are able to sustain their increased numbers.

big studies now under way:
Through Dr. Ernst Kuipers, my former postdoctoral trainee and now longtime friend, we were working with a group in the Netherlands to address this. A large cohort, including more than ten thousand mothers and their newborn children in Rotterdam, have been enrolled in the kind of study that could provide answers to important questions in development, but it will take several years for the kids to get old enough to have any reasonable outcome data. The United States is in the early stages of the National Children’s study, whose goal is to enroll up to one hundred thousand children, get lots of information, and see what kind of outcomes—especially asthma, obesity, and diabetes—they develop. The results of that study also will become available years from now.

Avon Longitudinal Study of Parents and Children (ALSPAC) study in Britain:
Drs. Leo Trasande and Jan Blustein, NYU faculty members who work primarily in pediatrics and health policy, respectively, are expert epidemiologists. They both found the ALSPAC Study (J. Golding et al., “ALSPAC—the Avon Longitudinal Study of Parents and Children, I. Study methodology,”
Paediatric and Perinatal Epidemiology
15 [2001]: 74–87) and led the analyses (L. Trasande et al., “Infant antibiotic exposures and early-life body mass,”
International Journal of Obesity
37 [2013]: 16–23; J. Blustein et al., “Association of caesarian delivery with child adiposity from age 6 weeks to 15 years,”
International Journal of Obesity
37 [2013]: 900–906).

may also contribute to the risk:
A Boston study of 1,255 mother-child pairs (S. Y. Huh et al., “Delivery by caesarean section and risk of obesity in preschool children: a prospective cohort study,”
Archives of the Diseases of Childhood
97 [2012]: 610–16) found a significantly increased obesity risk in offspring born by C-section. A Canadian study (K. Flemming et al., “The association between caesarean section and childhood obesity revisited: a cohort study,”
Archives of the Diseases of Childhood
98 [2013]: 526–32) showed that C-section was a risk factor overall, but when they controlled for excessive maternal weight it dropped out. Similarly in our ALSPAC study (J. Blustein et al.), nearly all of the risk was in babies born of mothers who already were overweight. There are many potential explanations for this; one is that the overweight mothers already have a depleted microbiota and C-section adds to the problem in the next generation. In Brazil, where in 2009 the C-section rate went above 50 percent, meaning that more than half the 3 million births in that country were by C-section, two studies showed different results. H. A. S. Goldani et al. (“Cesarean delivery is associated with an increased risk of obesity in adulthood in a Brazilian birth cohort study,”
American Journal of Clinical Nutrition
93 [2011]: 1344–47), studying a 1978 birth cohort twenty-three to twenty-five years later, found about a 50 percent increase in obesity in C-section babies that could not be explained by other factors. But F. C. Barros et al. (“Cesarean section and risk of obesity in childhood, adolescence, and early adulthood: evidence from 3 Brazilian birth cohorts,”
American Journal of Clinical Nutrition
95 [2012]: 465–70), studying three later birth cohorts, showed effects in the same direction, but they were not statistically significant. The authors discussed unaccounted confounding factors in their study. However, in a later study by the same authors (B. L. Horta et al., “Birth by Caesarean Section and Prevalence of Risk Factors for Non-Communicable Diseases in Young Adults: A Birth Cohort Study,”
PLOS ONE
8 [2013]: e74301), a follow-up of the 1982 birth cohort to the time of their entrance exam into the army at age eighteen (and with follow-up to age twenty-three), they found that C-section was associated with increased body mass index (BMI), amount of body fat, and also systolic blood pressure.