Previously unknown bacterial component in kidney stone formation
In an unexpected finding, a research 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 peer-reviewed journal PNAS, 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 the study’s co-senior author. “By uncovering this novel mechanism, the study opens the door to new therapeutic strategies that target the microbial environment of kidney stones.”
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 have been previously known to contain bacteria. While examining data from electron and florescence microscopy, the researchers unexpectedly detected live bacteria as well as layers, or biofilms, of bacteria integrated into the crystals.
The authors observed similar bacterial biofilm architectures on the surfaces of stone fragments obtained due to lithotripsy, suggesting that bacteria are intrinsic to the process of nephrolithiasis.
Crystallites proximal to biofilm layers exhibited significantly smaller grain sizes, which indicate a larger local concentration of nucleation sites. Staining reveals that biofilm areas of these stones are enriched with bacterial DNA.
“We found a new mechanism of stone formation that may help to explain why these stones are so common” the author said. “These results may also help to explain the connections between recurrent urinary tract infections and recurrent kidney stone formation, and provides insights on potential future treatment for these conditions.”
The findings suggest that bacteria could also be involved in other kidney stone types, the author added.
The study has 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.
“Our multi-institutional team is currently performing studies to determine how bacteria and calcium-based kidney stones interact. We want to understand exactly what makes some patients particularly susceptible to recurrent stone formation, and what it is about these particular species of bacteria that allows them to nucleate these stones,” the author said.
https://www.pnas.org/doi/10.1073/pnas.2517066123
https://sciencemission.com/bacterial-biofilms-in-kidney-stones
