Microbial Ecology in States of Health and Disease Workshop Summary (2014) / Chapter Skim
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A2 What are the consequences of the disappearing human microbiota?--Martin J. Blaser and Stanley Falkow
A2 What are the consequences of the disappearing human microbiota?--Martin J. Blaser and Stanley Falkow
Pages 110-130
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From page 110... ...
Blaser4 and Stanley Falkow5 Humans and our ancestors have evolved since the most ancient times with a commensal microbiota. The conservation of indicator species in a niche-specific manner across all of the studied human population groups suggests that the microbiota confer conserved benefits on humans.
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These properties imply that the microbiota have been selected, but it is becoming increasingly clear that although they are bounded by these rules they are also highly individual. The human microbiome is the subject of intensive studies, including the international Human Microbiome Project (Turnbaugh et al., 2007)
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One value of the Human Microbiome Project is that it can help us to ascertain how much the microbiota have been changing. Work is now ongoing, and the European Union and other countries are committed to similar projects, all work ing under the umbrella of the International Human Microbiome Consortium (see Further Information)
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. For example, several members of the nasopharyngeal microbiota, including Streptococcus pneumoniae and Neisseria meningitidis, regularly cause disease.
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Is there any underlying biological regulation that stabilizes the diverse microbial populations that we carry, even in the face of host immunity, competing organisms and the daily continuous flux of newly introduced microorganisms? Cooperation between competing life forms is a challenging concept and, although much of the literature on microorganisms focuses on the evolution of virulence (Maynard Smith and Szathmary, 1995; Messenger et al., 1997)
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The "Disappearing Microbiota" Hypothesis In general, it seems that the human microbiota and their hosts evolved their equilibria together, in an orderly way (Ley et al., 2008) , as diet, geography and occasional ecological disturbances had their effects on distinct, albeit diverse, human genetic backgrounds (Turnbaugh et al., 2009)
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Surprisingly, H pylori TABLE A2-1 Changes in Human Ecology That Might Affect Microbiota Composition Change Consequence Clean water Reduced faecal transmission Increase in Caesarean sections Reduced vaginal transmission Increased use of pre-term antibiotics Reduced vaginal transmission Reduced breast-feeding Reduced cutaneous transmission and a changed immunological environment Smaller family size Reduced early life transmission Widespread antibiotic use Selection for a changing composition Increased bathing, showering, and use of Selection for a changing composition antibacterial soaps Increased use of mercury-amalgam dental fillings Selection for a changing composition
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For humans, until recently, horizontal microbial transmission also occurred and could compensate for the loss of vertical transmission. Members of the microbiota were horizontally transmitted through faecally contaminated drinking and bathing water, and high physical contact as a result of social crowding and large families; in many modern societies, these routes have diminished.
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contribute to some of the diseases that are becoming more prevalent? The Human Microbiome Project (Turnbaugh et al., 2007)
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As H pylori is disappearing from human populations, reflecting both diminishing transmission and increasing antibiotic treatment (Table A2-1)
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The interaction of Helicobacter pylori with the gastric mucosa is representative of this model. The introduction of drugs, such as the commonly used proton pump inhibitors that reduce gastric acidity, affects equilibrium values and selects for a differing microbiota (Kanno et al., 2009; Vesper et al., 2009)
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. Subtherapeutic Antibiotic Treatment In the early 1950s, not long after the discovery of antibiotics, scientists found that feeding low doses of antibiotics (termed subtherapeutic antibiotic treatment [STAT]
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How is this affecting their microbiota, energy homeostasis and "feed efficiency"? Even single courses of widely used antibiotics can change the stable structure of microbial communities, with the presence of selected organisms continuing for years after the antibiotic exposure has ceased (Sjölund et al., 2003, 2005)
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. This can take place through direct competition or through microbial manipulation of host immunity (Lysenko et al., 2008; Regev-Yochay et al., 2009; Selva et al., 2009)
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in microbial transmission fitness. The second possibility is that the overall level of resident microorganisms will remain low, as other microorganisms cannot use the resources of the H
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This concept might be relevant to a range of inflammatory processes of the skin and mucosa, including inflammatory bowel disease and chronic periodontitis. It suggests that studies of pathogenesis should consider the general properties of microbial communities, such as resilience, or conserved functional interactions, such as syntrophic interactions and the importance of gene transfer, rather than the role of single microorganisms, especially for the development of new approaches for maintaining or restoring health.
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fcgi? db=genomeprj Further Information Human Microbiome Project: http://nihroadmap.nih.gov/hmp International Human Microbiome Consortium: http://www.human-microbiome.
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et al. Effect of the 7-valent pneumococcal conjugate vaccine on nasopharyngeal coloni zation by Streptococcus pneumoniae in the first 2 years of life.
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et al. Long-term effect of pneumococcal conjugate vaccine on nasopharyngeal coloniza tion by Streptococcus pneumoniae and associated interactions with Staphylococcus aureus and Haemophilus influenzae colonization in HIV-infected and HIVuninfected children.
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et al. Does pneumococcal conjugate vaccine influence Staphylococcus aureus car riage in children?
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et al. The human microbiome project.
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