Virulence of ureaplasmal urease for mice.

Ureaplasmas killed mice within 5 min after intravenous injection. The 50% lethal dose of whole ureaplasmal organisms was 32 micrograms per mouse, a value also found for crystalline jackbean urease. The reaction was specific to urease, since protection was afforded by intraperitoneal injection of 200 micrograms of flurofamide, a potent urease inhibitor. The finding that a similar lethal effect was produced by injection of 200 mumol of NH4+ indicates that the toxicity of urease is mediated by ammonium ions or free ammonia.