Abstract
The virulence of Salmonella choleraesuis subspecies choleraesuis serovar enteritidis (S. enteritidis) AL1192, a plasmid-cured derivative from virulent S. enteritidis AL1190, was tested. Except for fever no serious adverse clinical signs were observed in the 4 cattle inoculated subcutaneously or intravenously with S. enteritidis AL1192, although two of them showed positive fecal cultures. Next, it was also investigated that this strain was capable of protecting 7-month-old cattle against subsequent intramuscular challenge with Salmonella choleraesuis subspecies choleraesuis serovar typhimurium (S. typhimurium) L-535 of which O antigenic structure has common component with S. enteritidis AL1192. S. typhimurium L-535 used as a challenge strain was not fully virulent to the cattle in this experiment, even though it was isolated from mesenteric lymph node of a dead calf with salmonellosis and fully virulent to ddY mice. This prevented us from evaluating S. enteritidis AL1192 as a vaccine. This observation suggests that symptoms in 7-month-old cattle are not invariably observed although young calves are very susceptible to Salmonella. Moreover, S. enteritidis AL1192 could not prevent even infection with the challenge strain which was not so virulent for the aged cattle, judging from the development of specific H antibody against challenge strain.
