Problem statement: Recently, Salmonella hadar has been isolated and identified from goatin Iraq. The purpose of the present study was to investigate the ultrastructural changes in the ileumepithelial cells of mice experimentally infected with Salmonella hadar. Approach: The white BALB/cmice inoculated orally with Salmonella enterica serovar hadar strain and their ileums were examinedby transmission electron microscopy at 24, 48, 72, 96 and 120 h after inoculation. Results: Thechallenge organism appeared adhered to the mucosal microvilli of the ileum from 24 h postinoculation.The early ultrastructural changes characterized by local derangement with slight swellingof the proximal ends of the microvilli. In addition, there was ruffling of the apical cell surfaces of themicrovilli with cytoplasmic vacuolization of enterocytes due to invading by the organisms. TheChallenge organism was usually intact and enclosed by a membrane. The damage of the epithelial cellsstarted as a minor lesion at 24 h and became severe after 48, 72 and 96 h post infection. The more severeultrastructural changes in the ileum occurred at 120 h post infection, which revealed hypertrophy ofgoblet cell, dilatation of endoplasmic reticulum, severe cytoplasmic vacuolization, thickening of thenuclear membrane and several Salmonella Containing Vacuoles (SCV). Conclusion: Our resultsrevealed that the cellular invasion by Salmonella hadar may occurred early than 24 h because of theobvious alterations seen in the cells of the ileum at this time of infection. In addition, the continuationof cellular pathological changes for 120 h post infection may refers that S. hadar has somemechanisms which aid it to survive and replicate within intestinal cells. We recommend further studieswith early observation periods in order to determine the invasion time.
