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Last Updated: Apr 20, 2011 - 9:38:09 AM |
Contact: Diana Kenney, Marine Biological Laboratory, 508-428-2722; [email protected]
Antibiotics
Can Cause Pervasive, Persistent Changes to the Microbial Community in
the Human Gut, MBL and Stanford Scientists Report
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Mitchell Sogin
The Sogin Lab
Citation:
Dethlefsen,
L., S. Huse, M.L. Sogin, and D.A. Relman (2008). The pervasive effects
of an antibiotic on the human gut microbiota, as revealed by deep 16S
rRNA sequencing.
PloS Biology, #08-PLBI-RA-2095R2.
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MBL, WOODS HOLE, MA—Using a novel technique developed by Mitchell Sogin
of the Marine Biological Laboratory (MBL) to identify different types
of bacteria, scientists have completed the most precise survey to date
of how microbial communities in the human gut respond to antibiotic
treatment.
Sogin, director of the MBL’s Josephine Bay Paul Center, and Susan Huse
of the MBL, along with David Relman and Les Dethlefsen of Stanford
University, identified pervasive changes in the gut microbial
communities of three healthy humans after a five-day course of the
antibiotic Ciprofloxacin. Their results are reported in the Nov. 18
issue of
PloS Biology.
Using very conservative criteria, the scientists identified at least
3,300 to 5,700 different taxa (genetically distinct types) of bacteria
in the human distal gut, and antibiotic treatment influenced the
abundance of about a third of those taxa.
“You clearly get shifts in the structure of the microbial community
with antibiotic treatment,” says Sogin. “Some bacteria that were in low
abundance prior to treatment may become more abundant, and bacteria
that were dominant may decrease in abundance. When you get these
shifts, they may be persistent. Some individuals may recover quickly,
and others won’t recover for many months.”
In all the individuals tested in this study, the bacterial community
recovered and closely resembled its pre-treatment state within four
weeks after the antibiotic course ended, but several bacterial taxa
failed to recover within six months.
This raises questions about the health effects of perturbations to the
human-microbial symbiosis in the gut, such as may occur with antibiotic
treatment. Because specific microbial populations mediate many chemical
transformations in the gut—and previous studies have related these
processes to cancer and obesity, among other conditions—changes in the
composition of the gut microbiota could have important, but as yet
undiscovered, health effects.
“When you change the microbial population structure in the gut, you may
affect how that population is keeping indigenous pathogens at
manageable levels,” says Sogin. Bacteria that do not normally cause
problems may begin to grow more rapidly, and cause disease.
The study is part of a large, international effort to fully
characterize the microbiota in the human gut, which is the
highest-density natural bacterial ecosystem known. Up to 100 trillion
microbial cells reside in the gut, and this community plays essential
roles in nutrition, development, metabolism, pathogen resistance, and
regulation of immune responses.
Until recently, descriptions of human-associated microbiota were
constrained by techniques of cultivating (and thus identifying)
bacteria. Less than 20-40% of the microbes in the human distal gut, for
example, have been cultured in the laboratory. Since the late 1980s,
however, cultivation-independent microbial surveys have been developed
that identify community members by genetic sequencing. Sogin’s
technique, for example, which was used in this study, characterizes
microbial populations by pyrosequencing short, hypervariable regions of
one gene common to all microbes, the 16S rRNA gene. This technique
reveals greater taxonomic richness in microbial samples at a fraction
of the cost of traditional sequencing technologies.
The
MBL is a leading international, independent, nonprofit institution
dedicated to discovery and to improving the human condition through
creative research and education in the biological, biomedical and
environmental sciences. Founded in 1888 as the Marine Biological
Laboratory, the MBL is the oldest private marine laboratory in the
Western Hemisphere. For more information, visit www.MBL.edu.
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