Relationship of Serum Beta-glucuronidase and Lysozyme to Pathogenesis of Tularemia in Immune and Nonimmune Rats

A temporal study is reported of the febrile responses, tissue bacterial contents, and serum concentration of the lysosomal enzymes, beta-glucuronidase and lysozyme, in nonimmune rats inoculated with virulent or attenuated strains of Francisella tularensis, and in immune rats challenged with either a high or low dose of virulent organisms. The level of serum beta-glucuronidase appears to be an indicator of hepatocyte damage, whereas serum lysozyme correlates with the appearance, frequency, and severity of pyogranulomatous lesions. Survival of nonimmune rats after a challenge with either virulent or attenuated organisms appears to depend on a balance between dose of bacterial inoculum, celerity of irreversible pathologic events, and the ability of the reticuloendothelial and immune systems to collaboratively mount a response to limit or prevent dissemination of the infection. In immune rats, infection of parenchymal hepatic cells does not occur after a low dose (10-4) virulent challenge. Infection of parenchymal hepatic cells, however, does occur in immunized rats when the challenge dose is sufficiently large (10-8) so as to overcome the capacity of the reticuloendothelial to clear opsonized organisms.