Porcinein vitroandin vivomodels to assess the virulence ofSalmonella entericaserovar Typhimurium for pigs

Abstract

Salmonella Typhimurium infections in pigs pose an important human health hazard. One promising control measure is the development of live attenuated vaccine strains using defined knockout mutants. Preferably, screening of candidate knockout vaccine strains for attenuation should first be done in models allowing testing of a large number of strains. Thereafter, a limited number of selected strains should be further characterized in an experimental infection model in pigs. The aim of the present study was to develop such models. The invasive and proliferative characteristics of S. Typhimurium were assessed in both a non-polarized and a polarized porcine intestinal epithelial cell line. Neutrophils obtained from porcine blood were used to study the capacity of Salmonella to withstand killing by these phagocytes. The ability to induce an intestinal inflammatory response was investigated in a terminal intestinal loop model. The systemic phase of infection was mimicked by studying the uptake and intracellular survival of S. Typhimurium in porcine pulmonary alveolar macrophages and peripheral blood monocytes. These models should allow screening for attenuated strains. For further characterization, an experimental infection model was established, providing extensive data on the course of an oral infection and the optimal time points for colonization (day 5 postinoculation [ pi]) and persistency (days 21-28 pi) in pigs. In conclusion, screening for virulence of S. Typhimurium strains with subsequent confirmation for a subset of strains in a well-defined experimental infection model would significantly reduce the number of experimental pigs required.

The IPEC-J2 Cell Line

“…IPEC-1 and IPEC-J2 cells were both isolated from one day old piglets, whereas IPI-2I cells were isolated from an adult boar (Berschneider 1989 ). Furthermore, IPEC-J2 cells, unlike IPI-2I cells, form a polarized monolayer, promoting S. typhimurium invasion and replication (Boyen et al 2009 ).…”

“…An increasing number of studies use IPEC-J2 cells to investigate interactions of various animal and human pathogens, including Salmonella enterica and pathogenic Escherichia coli (Boyen et al 2009 ;Veldhuizen et al 2009 ). Pathogenic permeation (e.g.…”

Salmonellosis in swine: Clinical perspectives

“…Live vaccine strains consist of strains that are attenuated, strains with a mutation in genes that are important for bacterial metabolism, or strains in which specific virulence genes are removed (Kramer et al, 1992;Lumsden and Wilkie, 1992;Mastroeni et al, 2001;Boyen et al, 2009;Schwarz et al, 2011).…”

Controlling Salmonella infections in pig farms: A framework modelling approach

“…In short, S. Typhimurium is usually observed in pigs as a subclinical infection that produces no overt symptoms. However, when pigs are challenged with large doses of the pathogen they may develop an acute/high propagation syndrome with clinical symptoms (Boyen, Haesebrouck, Maes, Immerseel, Ducatelle and Pasmans, 2008;Boyen, Pasmans, Immerseel, Donn, Morgan, Ducatelle et al, 2009;Fravalo, Cariolet, Proux and Salvat, 2003;Loynachan & Harris, 2005;Griffith et al, 2006). Thus, the model includes two syndromes: a high propagation and a low propagation syndrome.…”