Live-Attenuated Oral Vaccines to Reduce Campylobacter Colonization in Poultry

The control of Campylobacter in poultry at the pre-harvest level is critical to reducing foodborne infections with Campylobacter since the consumption of contaminated poultry is the most frequent cause of human campylobacteriosis. Although poultry vaccination is suggested as useful intervention measures, no Campylobacter vaccines are currently available. To develop live-attenuated oral Campylobacter vaccines, in this study, we evaluated the efficacy of pre-colonization by oxidative stress defense mutants, including knockout mutants of ahpC, katA, and sodB, in preventing Campylobacter jejuni from colonizing poultry. Interestingly, when chickens were pre-colonized with ∆ahpC and ∆katA mutants, rather than the ∆sodB mutant, the level of C. jejuni colonization was significantly reduced within 35 days. Further studies demonstrated when chickens were pre-colonized with the ∆ahpC mutant by oral challenge with a high dose (ca., 5 × 10⁸ CFU/bird) and a low dose (ca., 5 × 10⁶ CFU/bird), it twice reduced the level of C. jejuni by 3.9 log₁₀ CFU/g feces and 3 log₁₀ CFU/g feces after 42 days, respectively, compared to the untreated control. Due to a colonization defect, the ∆ahpC mutant was removed from chickens within 42 days. After excretion from the host, moreover, the ∆ahpC mutant cannot survive in aerobic environments because of compromised aerotolerance. Our findings suggest that the ahpC mutant has a great potential for on-farm application to control C. jejuni at the pre-harvest level.