Early Epithelial Invasion bySalmonella entericaSerovar Typhimurium DT104 in the Swine Ileum

Abstract

Abstract. Salmonella enterica serovar Typhimurium is an important intestinal pathogen in swine. This study was performed to document the early cellular invasion of Salmonella serovar Typhimurium in swine ileum. Ileal gut-loops were surgically prepared in ten 4-to 5-week-old mixed-breed pigs and inoculated for 0-60 minutes. Loops were harvested and prepared for both scanning and transmission electron microscopy (SEM and TEM, respectively). Preferential bacterial adherence to microfold cells (M cells) was seen within 5 minutes, and by 10 minutes bacterial invasion of the apical membrane was seen in M cells, goblet cells, and enterocytes. This multicellular invasion was observed throughout the course of infection. In addition, SEM revealed a specific affinity of Salmonella serovar Typhimurium to sites of cell extrusion. Using TEM, bacteria in these areas were focused in the crevices formed by the extruding cell and the adjacent cells and in the cytoplasm immediately beneath the extruding cell. Our results suggest that early cellular invasion by Salmonella serovar Typhimurium is nonspecific and rapid in swine. Furthermore, the combination of SEM and TEM data suggests that Salmonella serovar Typhimurium may use sites of cell extrusion as an additional mechanism for early invasion.

Ultrastructural Changes in the Ileum of White BALB/C Mice Experimentally Infected with Salmonella hadar

“…The fragmentation and vesiculation of microvilli may be due to increases in cytoplasmic Ca 2+ concentration hich lead to the actin filaments of the microvillus core cytoskeleton to be broken into short filament as mentioned previously (Embaye et al, 1989). The ultrastructural changes was observed in the epithelial cells were probably due to the presence of many intracellular Salmonella that produced cytotoxin inside the cells, these observations is similar to that observed previously in the small intestinem of the rat infected experimentally with S. typhimurium (Naughton et al, 1996) and also with that found in the ileum of swine which infected with S. typhimurium DT104 (Meyerholz et al, 2002). The loss of microvilli reduced the intestinal absorption surface, this together with the functional deficiency and destruction of many epithelial cells, lead to decrease in the absorption and caused gastroenteritis and diarrhea.…”

Gene expression response of the rat small intestine following oral Salmonella infection

“…Based on these results, it seems that the IM is at least as important as the PP as the major site of early Salmonella invasion. This enterocyte-targeted invasion of Salmonella has also been reported in experiments with calves (14), pigs (27), and rabbits (57).…”

Characterization of Salmonella enterica serovar Typhimurium DT104 invasion in an epithelial cell line (IPEC J2) from porcine small intestine

“…This time-related pattern in bacterial invasion is similar for other strains of S. Typhimurium examined in some lines of intestinal and non-intestinal cultured epithelial cells (Francis et al, 1992;Kusters et al, 1993;Mills and Finlay, 1994). Invasion of S. Typhimurium into enterocytes is detectable as early as 5-10 min after inoculation into porcine small intestinal loops (Meyerholz and Stabel, 2002;Schauser et al, 2004). In contrast to the number of organisms recovered from gentamicin-treated cells, the total number of salmonellae recovered from cell monolayers that were not treated with the antibiotic (representing both adherent and internalized organisms) remained relatively high and increased to a lesser extent over this time interval.…”