A new method using a bacterium for dissolution of urinary stones.

PURPOSE: A bacterium, Thiobacillus thiooxidans, oxidizes inorganic sulfur compounds to sulfuric acid to obtain energy for growth. We examined dissolution of urinary stones by the bacteria and studied optimal conditions for the dissolution in human urine.

METHODS: Thiobacillus thiooxidans (IFO No. 13 701) was purchased from Hakko Kenkyujyo, Co., Osaka, Japan. The bacteria were grown stationary for 7 days at 30 degrees C in medium. The pH of the medium was changed from pH 4.82 to 1.95 for 28 days. Growth of the bacteria was also examined in human urine by addition of different amounts of sodium thiosulfite. The dissolution of human urinary stones was examined in the bladder of Wistar rat containing the bacteria (1 x 10(8)) for 7 days. 20 ml of 5 % sodium thiosulfite were injected intraperitoneally once a day. Histological changes of urinary tracts and blood test were also examined. As a control, two rats were examined in the same methods without the bacteria.

RESULTS: The number of bacteria was increased in human urine depending on the concentration of sodium thiosulfite. Among different kinds of urinary stones, calcium phosphate stone was most dissolved, 78 % reduction of dry weight in the rat bladder. Calcium oxalate, uric acid and magnesium phosphate stones were not well dissolved. But the stone weights in the control rats were increased twice. Slight inflammation was found in the rat bladder. There were no abnormal findings in the blood test.

CONCLUSIONS: Thiobacillus thiooxidans can be used for dissolution of urinary stones. This new technique may be useful for dissolution of fragments after ESWL and crystals covered by a urinary stent. Optimal conditions and safety methods should be developed for clinical use.