The incidence of kidney stones is on the rise worldwide, with 1 in 11 people expected to develop a stone at some point. There are several subtypes of kidney stones, with calcium oxalate (CaOx) stones occurring in more than 70% of cases. Recent research found live bacteria in calcium oxalate stones, along with biofilms.
Biofilms are communities of bacteria sticking to one another and coated with a protective slime. In these kidney stones, the biofilms were in-between mineral layers. Several bacterial species were most common in the kidney stones: E. faecalis, P. mirabilis, and E. coli.
Prior to this study, calcium oxalate kidney stones were not considered bacterial. The researchers thought that the bacteria might explain why people tend to have recurrent kidney stones.
Kidney stones begin as tiny crystals that can accumulate and clump together in urine. One easy way to decrease risk of developing kidney stones is do drink plenty of water (want to dilute your urine). Low fluid intake and dehydration is associated with increased kidney stone formation, due to concentrated urine.
An interesting earlier study looked at the microbiome of the kidneys and found that the beneficial bacteria L. crispatus is found in the absence of kidney stones, while the presence of E.coli was associated with the development of kidney stones. The researchers found that the L. crispatus somehow blocked E.coli's ability to form kidney stones.
From Medical Xpress: Previously unknown bacterial component in kidney stone formation discovered
In an unexpected finding, a UCLA-led team has discovered that bacteria are present inside the most common type of kidney stone, revealing a previously unrecognized component involved in their formation.
The findings, to be published in the journal Proceedings of the National Academy of Sciences, point to a possible therapeutic target that could be used for prevention and treatment for the millions of people who are affected by the frequently painful condition.
"This breakthrough challenges the long-held assumption that these stones develop solely through chemical and physical processes, and instead shows that bacteria can reside inside stones and may actively contribute to their formation," said Dr. Kymora Scotland, an assistant professor of urology at the David Geffen School of Medicine at UCLA and the study's co-senior author.
Kidney stones are composed of clumps of small crystals. Their prevalence has risen globally in recent years, so that today about 1 in 11 people will get them in their lifetime. Risk factors include family history, metabolic syndrome, and low fluid intake. The stones start forming when crystals grow in urine and become large enough that they can't be washed out with normal urine flow.
There are several subsets of kidney stones and while one rare stone type is known to contain bacteria, by far the most common stone is calcium oxalate (CaOx), comprising almost 80% of kidney stone cases, which have not been previously known to contain bacteria. While examining data from electron and fluorescence microscopy, the researchers unexpectedly detected live bacteria as well as layers, or biofilms, of bacteria integrated into the crystals.
"We found a new mechanism of stone formation that may help to explain why these stones are so common," Scotland said. "These results may also help to explain the connections between recurrent urinary tract infections and recurrent kidney stone formation, and provide insights on potential future treatment for these conditions."
The findings suggest that bacteria could also be involved in other kidney stone types, she added.
The study focused on calcium-based stones. How other less common stones form is still in question. More studies are needed to fully understand how bacteria and calcium-based kidney stones interact, the researchers conclude.