The importance of prolonged incubation for the synthesis of dimethylnitrosamine by enterobacteria.

Tests with 140 strains representing Escherichia coli, Klebsiella aerogenes, K. ozaenae, Proteus mirabilis, P. vulgaris, P. rettgeri and P. morganii in a defined medium supplemented with 0-09M dimethylamine (DMA) and 0-1M potassium nitrate showed that at least 89% of the 136 strains able to reduce nitrates produced up to 9mM dimethylnitrosamine (DMN) in 70h at 37 degrees C. Four nitratase-negative strains produced DMN from DMA in the presence of sodium nitrate. Prolonged incubation was the most important factor in determining DMN production. Stasis and persistent infection in the urinary tract, by simulating prolonged incubation of a culture, may be of importance in determining whether the potential carcinogen, DMN, could be produced in vivo by bacterial action on DMA and nitrate in urine.