Salmonella DNA adenine methylase mutants elicit protective immune responses to homologous and heterologous serovars in chickens

Salmonella DNA adenine methylase (Dam) mutants that lack or overproduce Dam are highly attenuated for virulence in mice and confer protection against murine typhoid fever. To determine whether vaccines based on Dam are effica cious in poultry, a Salmonella Dam(-) vaccine was evaluated in the protecti on of chicken broilers against oral challenge with homologous and heterolog ous Salmonella serovars. A Salmonella enterica serovar Typhimurium Dam- vac cine strain was attenuated for virulence in day-of-hatch chicks more than 1 00,000-fold. Vaccination of chicks elicited cross-protective immune respons es, as evidenced by reduced colonization (10- to 10,000-fold) of the gastro intestinal tract (ileum, cecum, and feces) and visceral organs (bursa and s pleen) after challenge with homologous (Typhimurium F98) and heterologous ( Enteritidis 4973 and S. enterica O6,14,24: e,h-monophasic) Salmonella serov ars that are implicated in Salmonella infection of poultry. The protection conferred was observed for the organ or the maximum CFU/tissue/bird as a un it of analysis, suggesting that Dam mutant strains may serve as the basis f or the development of efficacious poultry vaccines for the containment of S almonella.