Listeria monocytogenes isolates were intraperitoneally administered into the mice to evaluate the histopathological changes in various organs of the infected mice. The study consisted of nine groups of mice each group comprising of three mice. Inocula prepared from seven different isolates of Listeria monocytogenes were administered into seven different groups. The study also included one positive control (inoculated with reference strain) and one negative control (inoculated with normal saline) groups. The total period of study was 10 days. The pathogenicity of isolates and the reference strain was studied by injecting a fixed dose of organisms intraperitoneally into mice. The death of mice occurred between 2nd to 6th post exposure day. Four isolates killed more than 50% of mice, two isolates killed more than 30% of mice where as one isolate caused no death. The histopathological examination revealed more severe changes in liver and included microabscesses. The section of kidneys of infected mice revealed mild focal vacuolar degeneration in cortical epithelial cells. The sections of spleen, myocardium and brain also revealed altered histopathogical changes.

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