BCG-induced Susceptibility of Mice to Challenge with Pseudomonas aeruginosa

Abstract

Mice infected with Mycobacterium bovis, BCG, were shown to be highly susceptible to subsequent challenge with Pspdomonas aeruginosa. The susceptibility was characterized by the enhanced mortality and shoptened survival afteq challenge with P. aeruginosa. BCG-treated mice did not show any enhanaed susceptibility to challenge with Gram-positive bacteria such as Staphylococcus aureus or Liskria monocytogenes. BCG-treated mice eliminated P . aeruginosa from their organs in a pattqrn similar to that in untreated mice. There was no significant difference in the bactericidal activities of polymorphonuclear cells and macrophages between BCG-treated and untreated mice. An equal amount of endotoxin was detected by the Limulus lysate assay in the blood of both BCG-treated and untreated mice after challenge with P . aeruginosa. The enhanced susceptibility induced by BCG pretreatment could be decreased when the mice were rendered LPS-tolerant by injections of small amounts of LPS. These results suggest that BCG-induced slusceptibility to P . Qeruginosa can be ascribed to an enhanced susceptibility to the lethal qffect of LPS produced by challenge bacteria, and not to the impairment of the ability to eliminate infected bacteria.