Role of catalase in Campylobacter jejuni intracellular survival

The ability of Campylobacter jejuni to penetrate normally nonphagocytic hos t cells is believed to be a key virulence determinant. Recently, kinetics o f C. jejuni intracellular survival have been described and indicate that th e bacterium can persist and multiply within epithelial cells and macrophage s in vitro. Studies conducted by Pesci et al. indicate that superoxide dism utase contributes to intraepithelial cell survival, as isogenic sod mutants are 12-fold more sensitive to intracellular killing than wild-type strains . These findings suggest that bacterial factors that combat reactive oxygen species enable the organism to persist inside host cells. Experiments were conducted to determine the contribution of catalase to C. jejuni intracell ular survival. Zymographic analysis indicated that C. jejuni expresses a si ngle catalase enzyme. The gene encoding catalase (katA) was cloned via func tional complementation, and an isogenic katA mutant strain was constructed. Kinetic studies indicate that catalase provides resistance to hydrogen per oxide in vitro but does not play a role in intraepithelial cell survival. C atalase does however contribute to intramacrophage survival. Kinetic studie s of C. jejuni growth in marine and porcine peritoneal macrophages demonstr ated extensive killing of both wildtype and katA mutant strains shortly fol lowing internalization. Long-term cultures (72 h postinfection) of infected phagocytes permitted recovery of viable wild-type C. jejuni; in contrast, no viable katA mutant bacteria were recovered. Accordingly, inhibition of m acrophage nitric oxide synthase or NADPH oxidase permitted recovery of katA mutant C. jejuni. These observations indicate that catalase is essential f or C. jejuni intramacrophage persistence and growth and suggest a novel mec hanism of intracellular survival.