A rat model of infection by Salmonella typhimurium or Salm. enteritidis

Abstract

Salmonellosis in the rat has many similarities with the disease in humans, with the ileum thought to be the main site of colonization/invasion in both species. Thus, the rat may be a useful way to study the mechanism of infection by these pathogenic bacteria. A series of infection trials carried out with Hooded Lister rats showed that a salmonella infection persisted for an extended period of time and that salmonellae bind to the small intestinal epithelium as early as 4 h after intragastric intubation. Reinfection from the large intestine may not therefore initially play a significant role in the salmonella infection process. The rat model may therefore provide a means to test in vivo interventionist strategies, designed to block binding of the pathogens in the gastrointestinal tract. Road, Bucksburn, Aberdeen A B 2 9SB. UK (r-niail pjn'j"@rri.sari.ar..uk/. 0 1996 The Society for Applied Bacteriology 652 P.J. NAUGHTON E T A L . Correspondence to: Palrick J. Niiughlon, Division iflNutriiionu1 Sciences, Romeit Resrurch Institutr. Greenbiirn

Lack of flagella disadvantages Salmonella enterica serovar Enteritidis during the early stages of infection in the rat

“…These changes would be consistent with the infiltration of polymorphonuclear leukocytes and other inflammatory cells into gut tissue and the release of inflammatory cells into the lumen, previously observed in vivo (Naughton et al, 1995(Naughton et al, , 1996a.…”

“…Enteritidis strains LA5 and S1400 colonized and invaded in a manner generally similar to that seen with other S. Enteritidis or S. Typhimurium strains (Naughton et al, 1995(Naughton et al, , 1996a(Naughton et al, , 2000Havelaar et al, 2001;Islam et al, 2000). Thus, there was rapid distribution throughout the gastrointestinal tract, translocation to the mesenteric lymph nodes and spread to the liver and spleen of the rats.…”

“…MPO levels in the rat small intestine were unchanged 24 h after infection with S. Enteritidis S1400 but were significantly elevated at 72 h. Intestine tissue water content and faecal elastase was also increased at 72 h. This suggests that active recruitment of neutrophils to the intestine (Darwin & Miller, 1999;Stein et al, 1998;Faro et al, 2000;Zimmerman & Granger, 1990;McCormick et al, 1995;Naughton et al, 1996a) may have occurred between 24 and 72 h p.i. These changes would be consistent with the infiltration of polymorphonuclear leukocytes and other inflammatory cells into gut tissue and the release of inflammatory cells into the lumen, previously observed in vivo (Naughton et al, 1995(Naughton et al, , 1996a.…”

“…Salmonella sp. colonize the whole gastrointestinal tract of the rat and cause disruption of the small intestine epithelium, epithelial cell hyperplasia and infiltration by inflammatory cells (Naughton et al, 1995(Naughton et al, , 1996a(Naughton et al, , 2000Havelaar et al, 2001;Islam et al, 2000). Invasion is mainly via the ileum; large numbers of salmonella reach the mesenteric lymph nodes and moderate numbers spread to and persist in the liver and spleen.…”

“…Rats continue to grow, albeit slowly, and death due to infection is rare, unless health or immune status or gut integrity has been compromised by other factors. Salmonellosis in the rat thus has many similarities to the self-limiting gastroenteritis-type infection common in humans and domesticated animals (Naughton et al, 1995(Naughton et al, , 1996a(Naughton et al, , 2000Havelaar et al, 2001;Islam et al, 2000). Defined fimbriae-(SEF14, SEF17, SEF21, pef and lpf) and/or flagella-deleted mutants of S. Enteritidis and their wild-type parent strains were tested in this infection model.…”