Effects of products of autolysis of tissue and urine on the viability, morphology, and antigenicity of Leptospira interrogans serovar pomona

Abstract

The effect of the products of autolysis on Leptospira interrogans serovar pomona was investigated in bovine kidney tissues and urine inoculated with this organism. No viable leptospires were found at 24 h or subsequently after inoculation of kidney tissues or urine. Leptospires and their soluble antigens were rapidly destroyed in tissues stored at 20 degrees C and could not be detected by the fluorescent-antibody test and the enzyme-linked immunosorbent assay. On the other hand, leptospires were detectable by dark-field microscopy and fluorescent-antibody test 38 days after addition to urine. The rate of destruction proceeded less rapidly in tissues stored at 4 degrees C. Under the conditions of this study, soluble leptospiral antigen levels decreased less rapidly than did the number of detectable leptospires. Similarly, breakdown of leptospires, demonstrated by dark-field microscopy and fluorescent-antibody test, progressed during the first 5 days after inoculation of urine, when levels of soluble leptospiral antigen remained constant. Although the number of intact leptospires was markedly reduced after freezing of tissues at -20 degrees C, soluble leptospiral antigen levels remained unaltered. Neither intact leptospires nor their soluble antigens were detected after preservation of tissues in Formalin. However, formolization of urine delayed the destruction of leptospires and increased the levels of soluble leptospiral antigen during at least the first 5 days after inoculation. These results indicate that assays such as the enzyme-linked immunosorbent assay should be useful for the detection of soluble leptospiral antigens in urine and in autolyzing tissues such as those taken from a bovine fetus aborted as a result of leptospiral infection.