Bacteria May Discourage Formation of Kidney Stones
Researchers hope to learn more about useful intestinal bugs
What’s up?
Researchers at the School of Public Health have identified bacteria that may help prevent the formation of kidney stones, hard, often painful masses created by crystals that separate from urine within the urinary tract. Under normal circumstances, chemicals contained in urine prevent the crystals from forming, but in some cases, the chemicals fail to act.
David Kaufman, an SPH professor of epidemiology and an associate director of the University’s Slone Epidemiology Center, was aware that several small studies suggested that people with the harmless intestinal bacteria Oxalobacter formigenes have a lower risk of developing kidney stones. In the most comprehensive study to date, he and his team of researchers at the Slone Center compared the levels of the bacteria in 247 patients with repeat episodes of kidney stones and in 259 patients who didn’t suffer from recurring kidney stones.
The scientists hypothesized that Oxalobacter formigenes metabolizes oxalate, which is found in the diet and in the body, and is otherwise indigestible. Most kidney stones are made up of calcium oxalate. The researchers wanted to test whether oxalate would be reduced in urine with the presence of the bacteria and thereby decrease the risk of kidney stones.
What was found:
Kaufmann found that patients who have a higher rate of Oxalobacter formigenes are 70 percent less likely to develop kidney stones, a finding that was consistent despite sex, age, race, ethnicity, and antibiotic use. The researchers were surprised to find that while the
results confirmed their hypothesis, there was no direct correlation between having the bacteria and also having a lower amount of urinary oxalate.
Why it matters:
“If we find that having this bacteria significantly reduces the risk of kidney stones, then people theoretically could be given the bacteria as a way to prevent kidney stones,” says Kaufman. “Our results provide an underpinning for doing additional research.”
Word to the wise:
Researchers have yet to prove how this works. “The evidence of the association with the reduced risk is strong,” Kaufman says, “but we want to be careful about not overinterpreting the results given this surprising finding with urinary oxalate and given that we don’t enough about how the bacterium behaves in the population.” At this point, the researchers don’t know how people acquire the bacteria or how long it stays in the body.
What’s next:
Kaufman says the next steps are additional studies to learn how and when people acquire Oxalobacter formigenes, how long it remains in the body, and what factors determine if people colonize it.
Where to find more:
The research was published in the March 2008 issue of the Journal of the American Society of Nephrology.
Amy Laskowski can be reached at amlaskow@bu.edu.
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