Groups of six, 10-week-old pigs were inoculated with 0.65 x 103, 0.65 x 106 or 0.65 x 109 colony-forming units (cfu) of Salmonella Cubana or Salmonella Derby and then monitored for eight weeks for the faecal excretion of Salmonella species and the presence of serum antibodies. Eight tissue samples were collected postmortem from each pig and analysed for Salmonella species. In general, the dose had a greater impact on the responses of the pigs than the serovar. However, in the groups inoculated with 0.65 x 106 cfu, S Cubana were excreted only by one pig during the first two days after infection, whereas the pigs inoculated with S Derby all shed the bacteria constantly for two weeks and then intermittently for several weeks. In the low dose groups none of the pigs excreted any detectable salmonella whereas all the pigs in both high dose groups shed salmonella constantly or intermittently throughout the eight weeks. All the 12 pigs inoculated with 0.65 x 106 or 0.65 x 109 cfu of S Derby seroconverted during the study period, whereas all the pigs inoculated with 0.65 x 103 remained seronegative. No serological response could be detected in the three groups of pigs inoculated with S Cubana. In the postmortem samples both serovars were re-isolated from the caecal contents and the colonic tissue, but the other organs and tissues were all negative except for one ileocaecal lymph node from a pig inoculated with 0.65 x 106 cfu of S Derby.
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