A
new study from National Institutes of Health scientists and their Thai
colleagues shows that a “good” bacterium commonly found in probiotic digestive
supplements helps eliminate Staphylococcus aureus, a type of bacteria
that can cause serious antibiotic-resistant infections. The researchers, led by
scientists at NIH’s National Institute of Allergy and Infectious Diseases
(NIAID), unexpectedly found that Bacillus bacteria prevented S. aureus
bacteria from growing in the gut and nose of healthy individuals.
“Probiotics
frequently are recommended as dietary supplements to improve digestive health,”
said NIAID Director Anthony S. Fauci, M.D. “This is one of the first studies to
describe precisely how they may work to provide health benefits. The
possibility that oral Bacillus might be an effective alternative to
antibiotic treatment for some conditions is scientifically intriguing and
definitely worthy of further exploration.”
Staphylococcus
infections cause tens of thousands of deaths worldwide each year.
Methicillin-resistant Staphylococcus aureus, or MRSA, is familiar to
many people as a cause of serious disease. Less well known is that S. aureus
often can live in the nose or gut without causing any harm. However, if the
skin barrier is broken, or the immune system compromised, these colonizing
bacteria can cause serious infections.
One
strategy to prevent Staph infections is to eliminate S. aureus
colonization. However, some decolonization strategies are controversial because
they require considerable amounts of topical antibiotics and have limited
success, partly because they target only the nose and bacteria quickly
recolonized from the gut.
The
scientists recruited 200 volunteers in rural Thailand for the study. This
population, they speculated, would not be as affected by food sterilization or
antibiotics as people in highly developed urban areas. The scientists first
analyzed fecal samples from each of the study participants for bacteria
correlated with the absence of S. aureus. They found 101 samples
positive for Bacillus, primarily B. subtilis — the type
found mixed with other bacteria in many probiotic products. Bacillus
bacteria form spores that can survive harsh environments and commonly are
ingested naturally with vegetables, allowing them to temporarily grow in the intestine.
The scientists then sampled the same 200 people for S. aureus in the gut
(25 positive) and nose (26 positive). Strikingly, they found no S. aureus
in any of the samples where Bacillus were present.
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