Effect of competitive exclusion treatment on colonization of early-weaned pigs by Salmonella serovar Choleraesuis

Robin C. Anderson, PhD; Larry H. Stanker, PhD; Colin R. Young, PhD; Sandra A. Buckley, DVM, MS; Ken J. Genovese; Roger B. Harvey, DVM, MS; John R. DeLoach, PhD; Nancy K. Keith, PhD; David J. Nisbet, PhD

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Objective: To assess the potential of two porcine-derivedcompetitive exclusion cultures to enhance colonization resistanceof early-weaned pigs to Salmonella serovar Choleraesuis.

Methods: Litters from three and two sows, respectively,were treated at birth and again at weaning with either of twoporcine-derived competitive exclusion cultures, one less diversethan the other. Another litter was treated as above with the leastdiverse competitive exclusion culture that had been supplementedwith Bacteroides thetaiotaomicron, a bacterium implicatedin effecting gut cell development. Three other litters servedas placebo-treated or untreated controls. All piglets were challengedat 15 days of age (1 day postweaning) with 106-107colony-forming units (CFU) of Salmonella Choleraesuis.Rectal swabs (collected daily post challenge) and specimens (collectedat necropsy 7-9 days postchallenge) were cultured for SalmonellaCholeraesuis to assess the incidence of fecal shedding and colonizationstatus of each piglet. Statistical analysis was not performedin this preliminary study due to the confounding of treatmenteffects with litter effects.

Results: There were fewer pigs shedding in litters thatreceived the competition exclusion culture. There were fewer pigletswith salmonellae culture-positive tonsils within the litters treatedwith either competitive exclusion culture. Salmonella Choleraesuiswas recovered from the ileocolic lymph nodes of all 32 of theplacebo-treated or nontreated piglets and from most but not allof the piglets treated with either of the competitive exclusioncultures. While the incidence of shedding of SalmonellaCholeraesuis was less for the litter treated with the least diversecompetitive exclusion culture that had been spiked with Bacteroidesthetaiotaomicron than for the controls, no other benefitswere observed with this treatment.

Implications: Competitive exclusion treatment of babypiglets may enhance colonization resistance to SalmonellaCholeraesuis, which may reduce the potential for horizontaltransmission of the host-adapted pathogen. However, in the absenceof statistical analysis, our interpretation should be consideredpreliminary.

Keywords: Salmonella, competitive exclusion treatment, colonization, early weaning

RIS citationCite as: Anderson RC, Stanker LH, Young CR, et al. Effect of competitive exclusion treatment on colonization of early-weaned pigs by Salmonella serovar Choleraesuis. J Swine Health Prod 1999;7(4):155-160.

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