Abstract

Objective: To investigate the histopathological changes of mouse mammary tissue damage in dose and durational pathogenicity of Staphylococcus aureus (S. aureus) inoculums. Methods: The minimal tissue inflammation dose of S. aureus inoculum was determined by inoculating the lactating mice mammary gland to observe the mortality rate at 24, 48, 72 and 96 h of infection for each inoculum dilutions. To study dose pathogenicity, lactating mice were divided into one control and four induced groups of 5 mice each. S. aureus inoculums doses of 0.8伊101, 1.4 伊102, 2伊102 and 2.8伊103 colony forming unit were inoculated to the induced groups II, III, IV and V respectively. Mice were sacrificed and mammary gland tissues were harvested after 48 h of infection. Similarly to study of durational pathogenicity, a dose of 2伊102 colony forming unit of S. aureus inoculums was inoculated to the induced groups II, III, IV and V respectively. Mice were sacrificed and mammary gland tissues were harvested after 24, 48, 72 and 96 h of infection. Body and mammary gland were weighed and histopathological responses of the tissue damage were observed for both dose and durational pathogenicity ’s of S. aureus inoculums. Results: The observations indicated mastitis symptoms, decrease in body and mammary gland weights. Histopathological evidences revealed massive infiltration of polymorphonuclear neutrophil leukocytes, damage of alveoli and secretory products as the doses and durations of S. aureus inoculum increased compared to the control. Conclusions: The present study revealed that damage in mammary gland tissue of mice increased as the dose and duration of S. aureus inoculums increased

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