The effect of plum juice on the prevention of struvite calculus formationin vitro

Study Type – Prevention (cohort) Level of Evidence 2b What's known on the subject? and What does the study add? Urinary struvite calculus is always related to urinary tract infections with urease-producing bacteria. Prevention strategies for struvite calculus have focused on urine sterilization, urine acidification and urease activity inhibition. The clinical utility of all the available agents remains limited with respect to long-term use because of serious side effects or antimicrobial resistance. Plum juice has shown antibacterial activity on the urease-producing bacteria Helicobacter pylori. Importantly, plums also showed an effect on urinary acidification in humans. The present study conducted in vitro reports a concentration-dependent inhibition of plum juice on urease activity, as well as antibacterial effects on four urease-producing bacterial commonly found in the urine of patients with struvite calculus. The results of the crystallization experiment perfomed in vitro showed that natural plum juice prevented the occurrence of Proteus mirabilis-induced crystals, whereas pH-adjusted plum juice slowed the growth rate of struvite crystals. OBJECTIVES • To evaluate the effect of plum juice on struvite calculus formation in vitro and to explore the effect of plum juice on urease-producing bacteria and urease activity • The compliance of available drugs is low for struvite calculus after surgical treatment and functional food may represent a good choice as an alternative therapy. MATERIALS AND METHODS • Antibacterial activity was assessed using a microdilution antimicrobial susceptibility test. • Urease activity was determined by measuring ammonia production. • Struvite crystals were induced by Proteus mirabilis in artificial urine with natural and pH-adjusted plum juice. • The optical density (OD)600 and pH of artificial urine were examined, as well the shape and weights of crystals. RESULTS • Natural plum juice showed an antibacterial effect on urease-producing bacteria, whereas the pH-adjusted juice did not. • A concentration-dependent inhibition on urease activity was found for both natural and pH-adjusted juice. • Natural plum juice at a high concentration of 0.5% showed an obvious inhibition on the increase of OD600 and pH of the artificial urine, and crystal formation was prevented by up to or more than 8 h, depending on the concentration of juice. • Crystal weight in the natural plum juice groups was decreased in a concentration-dependent manner. • The pH-adjusted plum juice did not show any effect on OD600 and pH, although the presence of juice changed the crystal habit, indicating that the juice slowed the growth rate of crystals. CONCLUSIONS • Natural plum juice at high and moderate concentrations prevented the formation of P. mirabilis-induced crystals for up to 8 h in artificial urine. Although pH-adjusted and low-concentration natural juice did not prevent the occurrence of crystals, both types of juice slowed their growth rate.