Dr Blaser began his lecture with a discussion of the conundrum of early life antibiotic exposure. Each and every human being on the planet has a plethora of microbial symbionts. These symbionts are ancient- all animal lineages have them, which is evidence for such symbiotic relationships having existed among the first animals to evolve. These symbionts are "niche"- different microbes thrive in different regions of the body, with oral bacteria differing dramatically from gut bacteria, skin bacteria, and urogenital bacteria. These symbionts are persistent and conserved- after infancy, an individual's interior biome becomes remarkably stable throughout one's life. Finally, these symbionts are host-specific. Each individual has a unique microbiome. Humans harbor more bacterial cells in their bodies than "human" cells. 70-80 percent of the cells present in and on the human body are microbes. Even more dramatically, 99 percent of the genes present in the human body are microbial genes.
Dr Blaser then discussed the effects of microbial symbionts during pregnancy. Throughout pregnancy, the microbiome changes. In a study of germ-free mice introduced to bacteria taken from the gastrointestinal tracts of women in the third trimester of pregnancy, the mice gained weight and exhibited "diabetic" traits. The gut bacteria of pregnant individuals seems to "mobilize" calories in such a manner to benefit the developing fetus. The bacterial symbionts have co-evolved with the host... such coevolution can been likened to a dialogue between the host and its microbes. One of Dr Blasers main areas of inquiry is what happens when this relationship is perturbed.
A disappearing microbiota results in a changing human ecology- altered microbe composition affects physiology. The early microbiome affects development, with early antibiotic exposure correlating with the incidence of obesity. The geography of obesity and the geography of antibiotic use correlates in a very suggestive manner. It has long been known that subtherapeutic use of antibiotics will promote growth in farm animals. The earlier in life this antibiotic use occurs, the more efficient its results.
Studies indicated that the subtherapeutic antibiotic treatment (STAT) will result in greater muscle mass. Add fat to STAT, and the antibiotics pontentiate fat gain. A study was performed to determine if increased adiposity was durable with limited antibiotic exposure- administration of antibiotics for four weeks was sufficient to cause long-term adiposity. In subjects exposed to antibiotics from birth, the weight gain was more pronounced. Mice exposed to early antibiotic "treatments" down-regulated their immune systems. With time, the "fecal community" of microbes can revert to normal after the cessation of antibiotic exposure, but the effects on body mass are permanent. Antibiotic exposure need not be persistent- "pulse" doses of antibiotics are sufficient to affect immunity.
During development, an organism's stem cells receive signals from its microbial symbionts. In early life, there is a more diverse microbiome, which tends to stabilize as one grows into adulthood. One antibiotic dose can decrese microbial biodiversity, which can alter development. It is estimated that the population in the U.S. has lost 20% of its microbial biodiversity- antibacterial activities have "collateral damage".
Dr Blaser enumerated a plan to address the diminishing microbial biodiversity. Research about the consequences of overuse of antibiotics has to continue. Education about the risks of antibiotic overuse needs to proceed. The development of narrow-spectrum antibiotics which target deleterious microbes while doing minimal damage to helpful symbionts needs to be prioritized. Remediation of damaged internal biomes with probiotics needs to be promoted, with the reversal of the loss of biodiversity the end goal. Finally, the recovery of "lost" microbes needs to be investigated.
Once again, Dr Blaser delivered a thought-provoking lecture on a topic which has far-ranging implications on human health. In the Q&A session, he went into more depth on such subjects as fecal transplants. Some bastard in the audience asked about the implications of antibiotic overuse on autoimmune maladies. Dr Blaser indicated that a diminished internal biome has been implicated in some forms of asthma, and there are now studies concerning the role of a diminished microbiome in type one diabetes.
To get a taste of Dr Blaser's congenial lecturing style, here is the man himself being interviewed on The Daily Show:
For a more substantial interview, here is Dr Blaser's appearance on Leonard Lopate's radio show.
Needless to say, last night's lecture was yet another phenomenal presentation of the Secret Science Club. Here's a tip of the hat and a heartfelt thank-you to Dorian, Margaret, and the staff of the beautiful Bell House.
EDIT: Holy cats, I left out a crucial part of the lecture, having been rushed when I was composing this post. One of the most important items was a timeline of antibiotic development- as microbes evolved resistance to antibiotics (it's a simple matter of evolution- any bacteria not killed by an antibiotic will reproduce, and their descendents will be resistant). New antibiotics have been developed to counter microbial resistance, and the microbes would develop resistance to the new antibiotics. We are now at a stage where there are multiple-resistant strains of various microbes, with MRSA being a particularly pernicious example. Sorry about this lapse, folks!