IN-VIVO EFFECTS OF UREASE PRODUCING BACTERIA INVOLVED WITH THE PATHOGENESIS OF INFECTION-INDUCED UROLITHIASIS ON RENAL UROKINASE AND SIALIDASE ACTIVITY

Many hypotheses have been proposed for renal stone formation. It has b een argued that with infection-induced renal stones the hydrolysis of urea by bacterial urease increases urinary pH, with consequent stone f ormation. Unfortunately, this theory is not applicable to the micro-or ganisms that do not produce urease (e.g. Escherichia coli). It has bee n recently reported that E. coli reduces the urinary urokinase activit y of male rats, but does not influence the urinary sialidase activity. This study has now been expanded to the urease-producing bacteria Pro teus mirabilis, Staphylococcus aureus, S. epidermidis, Pseudomonas aer uginosa and Micrococcus luteus. Subcutaneous injections with these bac teria were found to significantly (P < 0.003) reduce the UK activity o f extrarenally obstructed kidneys. The urease-producing mammalian skin bacterium, M. luteus, was, however, the exception (P=0.1079). In cont rast to S. epidermidis, P. aeruginosa and M. luteus (P < 0.0213), P. m irabilis and S. aureus had no effect on renal sialidase activity (P < 0.4047). These results may explain why Proteus species are predominant in infection-induced renal stones. According to the urokinase-sialida se hypothesis, a decrease in urinary urokinase activity should increas e the uromucoid levels, whilst no effect on the urinary sialidase acti vity should favour conversion of urinary uromucoid to mineralizable ma trix. These conditions may lead to renal stone formation. An increase in urinary pH resulting from urease-producing micro-organisms will inc rease salt precipitation on the uromucoid. It is thus concluded that u rease-producing bacteria may play a double role in renal stone formati on.