American journal of veterinary research · 1996
Effect of dose on the immune response and persistence of Salmonella choleraesuis infection in swine.
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Gray J T, Stabel T J, Fedorka-Cray P J
Аннотация
OBJECTIVE: To establish the effect of dose on persistence of and immune response to Salmonella choleraesuis in swine.
DESIGN: 19 Salmonella-free pigs were allotted to 4 groups. Groups 1 (n = 5), 2 (n = 5), and 3 (n = 5) were inoculated intranasally with 10(9), 10(6), and 10(3) colony-forming units of S choleraesuis, respectively. Group 4 (n = 4) served as uninoculated controls.
PROCEDURE: Pigs were monitored for clinical signs of disease and bacterial shedding. Serum and lymphocytes were obtained to measure immune responses. Pigs from groups 1, 2, and 4 were necropsied at postinoculation (PI) weeks 6 and 15. Pigs from groups 3 and 4 were necropsied at PI weeks 6 and 10.
RESULTS: Pigs in group 1 shed S choleraesuis through PI week 15 and were tissue positive at PI weeks 6 and 15. Pigs in group 2 were tissue positive for S choleraesuis until PI week 6 and continued shedding through PI week 9. Salmonella choleraesuis was not recovered at any time from pigs in groups 3 or 4. Pigs in groups 1, 2, and 3 had serum IgG and IgM titers to S choleraesuis lipopolysaccharide and soluble antigens. Pigs in all groups had a lymphocyte response to concanavalin A, and pigs in groups 1 and 2 had a lymphocyte response to S choleraesuis endotoxin. Pigs in group 1 had a lower stimulation index in response to both antigens, indicating some form of lymphocyte immunosuppression.
CONCLUSIONS: Persistence of S choleraesuis in host tissues is dose dependent. Short-term persistence can occur after a dose as low as 10(6) colony-forming units of S choleraesuis. Higher doses result in development of long-term carrier status, which may be related to the observed lymphocyte immunosuppression.
DESIGN: 19 Salmonella-free pigs were allotted to 4 groups. Groups 1 (n = 5), 2 (n = 5), and 3 (n = 5) were inoculated intranasally with 10(9), 10(6), and 10(3) colony-forming units of S choleraesuis, respectively. Group 4 (n = 4) served as uninoculated controls.
PROCEDURE: Pigs were monitored for clinical signs of disease and bacterial shedding. Serum and lymphocytes were obtained to measure immune responses. Pigs from groups 1, 2, and 4 were necropsied at postinoculation (PI) weeks 6 and 15. Pigs from groups 3 and 4 were necropsied at PI weeks 6 and 10.
RESULTS: Pigs in group 1 shed S choleraesuis through PI week 15 and were tissue positive at PI weeks 6 and 15. Pigs in group 2 were tissue positive for S choleraesuis until PI week 6 and continued shedding through PI week 9. Salmonella choleraesuis was not recovered at any time from pigs in groups 3 or 4. Pigs in groups 1, 2, and 3 had serum IgG and IgM titers to S choleraesuis lipopolysaccharide and soluble antigens. Pigs in all groups had a lymphocyte response to concanavalin A, and pigs in groups 1 and 2 had a lymphocyte response to S choleraesuis endotoxin. Pigs in group 1 had a lower stimulation index in response to both antigens, indicating some form of lymphocyte immunosuppression.
CONCLUSIONS: Persistence of S choleraesuis in host tissues is dose dependent. Short-term persistence can occur after a dose as low as 10(6) colony-forming units of S choleraesuis. Higher doses result in development of long-term carrier status, which may be related to the observed lymphocyte immunosuppression.