Essential role for cyclic AMP and its receptor protein in Yersinia enterocolitica virulence

Insertion mutations were isolated in cya and crp of Yersinia enterocolitica, which encode adenylate cyclase and the cyclic AMP (cAMP) receptor protein (CRP). The cya and crp mutants were affected for the production of proteins exported by the Ysc, Ysa, and flagellar type III secretion systems (TTSS). Protein production by each TTSS was restored when the respective mutation was complemented by a plasmid-encoded copy of the wild-type gene. Both cya and crp mutants exhibited reduced virulence for orally infected BALB/c mice in a 50% lethal dose analysis. Examination of bacterial survival in host tissues showed that cya and crp mutants colonized Peyer's patches and, to a lesser extent, mesenteric lymph nodes. However, the mutants did not appear to disseminate to the liver and spleen of infected mice. An initial examination of the effectiveness of Y. enterocolitica cya and crp mutants to stimulate protective immunity against subsequent challenge with virulent bacteria in mice was promising. The results indicate that the cAMP-CRP regulatory system is required for Y. enterocolitica virulence.