Early epithelial invasion by Salmonella enterica serovar Typhimurium in the swine ileum

Abstract

<p>The purpose of the experiment was to define the early cellular invasion of Salmonella enterica serovar Typhimurium in a swine gut-loop model. Ileal gut-loops were surgically prepared in 4-5 week old pigs and inoculated with sterile media or Salmonella serovar Typhimurium for 0 to 60 minutes. Loops were harvested and prepared for both scanning and transmission electron microscopy. Preferential bacterial adherence to M cells was observed by 5 minutes postinoculation and apical invasion was seen in M cells, goblet cells and enterocytes by 10 minutes postinoculation. This nonspecific invasion was observed throughout the course of infection. The results suggest early invasion by Salmonella serovar Typhimurium is not cell-specific and calls into question the concept of cell-specific invasion sites. In addition, scanning electron micrographs showed a specific affinity by Salmonella serovar Typhimurium to sites of cell extrusion. Transmission electron micrographs depicted bacteria around and in the crevices formed by extruded cells and the adjacent cells, and in the cytoplasm immediately beneath extruded cells. The combination of scanning and transmission electron micrographs suggests Salmonella serovar Typhimurium may utilize sites of cell extrusion for early invasion in swine.</p>