Urease Positive and Slime Producing Bacterial Activity: Results in Gallstone Precipitation and Solidification

Background: Bacteria are commonly isolated from gallstones. Presence of bacteria in gallstones might play a role in their formation. Objectives: We aimed to study different properties of isolates from gallstones and their relationship with the mechanism of gallstone formation. Patients and Methods: This study included 526 subjects. Gallstones and bile samples of the patients were cultured. Isolates were identified by different biochemical tests and examined for their B-glucuronidase activity, slime production and Urease activity. Biostatistical analyses were done to determine the relationship between the biliary bacterial factors and the types of gallstones. Role of Slime and urease activity in mechanism of gallstone formation were tested in vitro. Results: Overall, 94.77% of the gallstones were found to be infected, of which 85% of the cholesterol stones, 97% of pigmented stones and 100% of mixed stones showed the presence of bacterial isolates (P < 0.0001). B-glucuronidase activity was associated with isolates from pigmented or mixed stones and completely absent in cholesterol gallstones (P = 0.018). Urease activity was basically associated with cholesterol gallstones (P < 0.0001) while slime (P < 0.0001) activity was not specific for any single type of stone formation yet isolates of bile had a significant association with slime activity. In vitro analysis demonstrated that bacteria with urease activity are involved in CaCO3 precipitation and slime-producing isolates solidify the precipitated CaCO3. Conclusions: B-glucuronidase activity is mainly responsible for pigmented gallstone formation. Urease activity was predicted to be involved in nucleation and slime production during solidification of gallstones, as observed during in vitro studies. Hence, presence of these bacterial factors may enhance gallstone formation.