Spontaneous proteus nephritis among male C3H/HeJ mice.

The spontaneous occurrence of nephritis and resultant mortality was investigated among 2,836 control or treated (dermal carcinogenesis bioassays) C3H/HeJ male mice. Overall incidence of nephritis putatively caused by Proteus mirabilis was 1.2%. Incidences were similar in control and treated mice and ranged from 2.5--32.5% among 73 unrelated treatment or control groups. Diagnosis was based upon characteristic gross or histologic renal lesions. Grossly affected kidneys contained either multiple, discrete tan foci or elevated pale tan patches. Histologic renal lesions consisted of a multifocal necropurulent nephritis with numerous gram negative bacteria present in affected tubules. Necrotizing pyelitis and papillitis usually was present, an necropurulent cystitis was present in half of the cases examined histologically. Proteus mirabilis, isolated in pure culture from an affected kidney, produced similar renal lesions after intraperitoneal or intravenous inoculation of clinically normal C3H/HeJ males. The organism was reisolated from the kidneys of the experimentally produced cases. It was concluded that nephritis putatively caused by Proteus mirabilis was an important cause of mortality in male C3H/HeJ mice.