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

Problem statement: Recently, Salmonella hadar has been isolated and identified from goat in Iraq. The purpose of the present study was to investigate the ultrastructural changes in the ileum epithelial cells of mice experimentally infected with 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 postinoculation. The early ultrastructural changes characterized 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 enterocytes 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 severe ultrastructural changes in the ileum occurred at 120 h post infection, which revealed hypertrophy of goblet cell, dilatation of endoplasmic reticulum, severe 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 continuation of cellular pathological changes for 120 h post infection may refers that S. hadar has some mechanisms which aid it to survive and replicate within intestinal cells. We recommend further studies with early observation periods in order to determine the invasion time.