URINARY NITRITE - MORE THAN A MARKER OF INFECTION

Objectives. The bacteriostatic gas nitric oxide (NO) is formed when ni trite is acidified. Infected urine may contain considerable amounts of nitrite as a result: of bacterial nitrate reductase activity, and det ection of nitrite in urine is routinely used in the diagnosis of bacte rial cystitis. We sought to determine whether NO was generated from ac idified nitrite-containing urine. Furthermore, we also studied the gro wth of the urinary pathogen Escherichia coli in acidified nitrite-cont aining urine. Methods. Urine, collected from healthy control subjects or from patients with infected nitrite-containing urine, was acidified and incubated in a closed syringe with varying amounts of nitrite add ed. After 30 minutes, the headspace gas was removed and immediately in jected into a chemiluminescence NO analyzer. In addition, NO was measu red in urine collected from healthy control subjects after ingestion o f vitamin C. Bacterial growth was measured continuously in control uri ne for 10 hours after incubation for 2 hours in acidic urine with vary ing concentrations of nitrite added. Results. Large amounts of NO were released from infected nitrite-containing urine after mild acidificat ion. NO was also released from acidified control urine if nitrite was added, and this release was greatly potentiated in the presence of vit amin C. Furthermore, the growth of E. coli was markedly reduced by the addition of nitrite to acidified urine. Conclusions. We propose that nitrite-producing bacteria induce their own death in acidic urine by s upplying substrate for generation of bacteriostatic compounds such as NO, This mechanism might explain why urinary acidification and vitamin C may be effective in the treatment of bacteriuria. (C) 1997, Elsevie r Science Inc. All rights reserved.