The association between bacteria and urinary stones

Urinary stone disease (USD) is an increasing clinical problem in both children and adults. One in ten individuals will experience a urinary stone, yet the mechanisms responsible for urinary stones remain largely unknown. Bacteria have long been recognized to contribute to struvite urinary stones; however, the role of bacteria in the development of the more common calcium oxalate (CaOx) and calcium phosphate (CaPhos) stones has not been extensively investigated. However, several findings do indicate a possible association between urinary stones and bacteria, including the high rate of urinary tract infections (UTI) in urinary stone patients and multiple case series of culture-positive urinary stones, including stones composed of CaOx or CaPhos. New technology, such as next generation sequencing, may be used to lend additional insight regarding the association between urinary stones and bacteria. In 2015, we published the initial bacterial sequencing results from five urinary stones, from which we sequenced multiple types of bacterial DNA. Whether these bacteria are causal, disease modifying or passively present remains to be determined. However, initial exploration of underlying mechanisms for this association indicate that bacteria aggregate selectively to crystals, that their presence is associated with increased clumping of crystals, and that they stimulate incorporation of proteins into the stone matrix.