Degree Type

Dissertation

Date of Award

1992

Degree Name

Doctor of Philosophy

Department

Veterinary Microbiology and Preventive Medicine

First Advisor

James A. Roth

Abstract

Carrier swine infected with Salmonella typhimurium provide a reservoir of infection for humans and domestic animals. Reduction of the carrier state is desirable, but little is known about the bacterial-host interactions that influence the carrier state in swine. Interactions of S. typhimurium and porcine neutrophils were examined, and the effect of a [delta]cya[delta]crp mutant of S. typhimurium on subsequent wild-type colonization of swine was evaluated;When compared to those from unexposed controls, neutrophils from pigs orally exposed to S. typhimurium demonstrated reduced oxidative metabolism, measured by cytochrome C reduction and iodination; reduced motility, measured by random migration and chemotaxis; and reduced antibody-dependent cell-mediated cytotoxicity (ADCC) 1-2 days after exposure. Function normalized after 3-4 days, but iodination and ADCC were depressed again 7-14 days after exposure. Neutrophil bactericidal activity against S. typhimurium was enhanced in Salmonella-infected pigs 1-14 days after exposure;Treatment of pigs with bacillus Calmette-Guerin (BCG) before exposure to S. typhimurium did not reverse Salmonella-induced alterations in neutrophil function nor did it alter the colonization pattern and persistence of S. typhimurium in porcine internal organs;Bactericidal efficiency of porcine neutrophils against S. typhimurium was affected by bacterial opsonization, incubation interval, bacterial mutations, and by pre-treatment of neutrophils with recombinant human tumor necrosis factor alpha (TNF[alpha]). Opsonization enhanced bactericidal efficiency 0.5-2 hours after exposure, but this enhancement was decreased or lost by 3-4 hours. A phoP mutation in S. typhimurium conferred increased sensitivity to bactericidal activity. TNF[alpha] treatment caused a decrease in bactericidal efficiency 0.5-1 hour after exposure to S. typhimurium. This inhibition diminished by 2-3 hours, and bactericidal efficiency of TNF[alpha]-treated neutrophils was enhanced over nontreated neutrophils by 4 hours;Oral exposure of swine to a [delta]cya[delta]crp mutant of S. typhimurium ([chi]4233) caused a mild fever and soft feces. However, pigs previously exposed to [chi]4233 exhibited a milder clinical response to subsequent wild-type challenge than did pigs not exposed to [chi]4233. Ileal populations of wild-type S. typhimurium in [chi]4233-exposed pigs were 100- to 10,000-fold less than those in pigs not receiving [chi]4233. The liver, spleen, and ileocolic lymph nodes were cleared of wild-type S. typhimurium more quickly in [chi]4233-exposed pigs.

DOI

https://doi.org/10.31274/rtd-180813-11399

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Nancy Ellen Coe

Language

en

Proquest ID

AAI9234799

File Format

application/pdf

File Size

94 pages

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