Abstract
Problem statement: Recently, Salmonella hadar has been isolated and identified from goat in Iraq. The purpose of the present study was to in vestigate the ultrastructural changes in the ileum epithelial cells of mice experimentally infected wi th Salmonella hadar . Approach: The white BALB/c mice inoculated orally with Salmonella enterica serovar hadar strain and their ileums were examined by transmission electron microscopy at 24, 48, 72, 96 and 120 h after inoculation. Results: The challenge organism appeared adhered to the mucosal microvilli of the ileum from 24 h post- inoculation. The early ultrastructural changes char acterized by local derangement with slight swelling of the proximal ends of the microvilli. In addition , there was ruffling of the apical cell surfaces of the microvilli with cytoplasmic vacuolization of entero cytes due to invading by the organisms. The Challenge organism was usually intact and enclosed by a membrane. The damage of the epithelial cells started as a minor lesion at 24 h and became severe after 48, 72 and 96 h post infection. The more sev ere ultrastructural changes in the ileum occurred at 12 0 h post infection, which revealed hypertrophy of goblet cell, dilatation of endoplasmic reticulum, s evere cytoplasmic vacuolization, thickening of the nuclear membrane and several Salmonella Containing Vacuoles (SCV). Conclusion: Our results revealed that the cellular invasion by Salmonella hadar may occurred early than 24 h because of the obvious alterations seen in the cells of the ileum at this time of infection. In addition, the continu ation of cellular pathological changes for 120 h post inf ection may refers that S. hadar has some mechanisms which aid it to survive and replicate wi thin intestinal cells. We recommend further studies with early observation periods in order to determin e the invasion time.
Highlights
Salmonella species are facultative intracellular gram-negative bacteria that cause a wide array of disease including systemic disease and enterocolitis in a multitude of hosts (Antunes et al, 2003)
Murine infection with Salmonella enteric serovar typhimurium has been used predominantly to model human typhoid, while bovine infection with Salmonella enterica serovar Dublin or S. enterica serovar typhimurium has been a prevailing model of intestinal disease. These models have been exploited to gain critical insight into the pathogenesis of disease cause by Salmonellae, including that invasion-associated genes are required for intestinal secretory and inflammatory disease, that intracellular survival in both the intestinal epithelium and macrophages is essential for systemic pathogenesis and that M cells of the ileal Peyer’s patches are the site of invasion for systemic infection in murine typhoid prior to dissemination to liver and spleen via the reticuloendothelial system (Naughton et al, 2001; Poppe, 1999; Rahman et al, 2000; Wehkamp et al, 2004)
The ileum of infected mice killed at 24 h post infection revealed different ultrastructural changes
Summary
Salmonella species are facultative intracellular gram-negative bacteria that cause a wide array of disease including systemic disease and enterocolitis in a multitude of hosts (Antunes et al, 2003). Four mice of each group were anesthetized at intervals 24, 48, 72, 96 and 120 h post infection and a part of small intestine (ileum) from both groups was taken for transmission electron microscope investigation.
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