Effects of Dexamethasone on Rats Infected with Pasteurella multocida
Two groups of Sprague-Dawley adult male rats each consist of 8 animals were used throughout the experiment. All rats were subcutaneous inoculated once with 108cfu/ml of Pasteurella multocida strain PMB 202. In addition, Group 1 animals also received intra-muscular injection of dexamethasone (1.6 mg/animal/day) once daily for 9 days. Blood was collected from all animals before and after inoculation once daily for 9 days, for total and differential leucocytes count. Rats were scarified at day 9 for swabs culture and histological sections of liver, spleen and lung. In dexamethasone-treated animals (Group 1), total leucocytes count decreased after 24 hours (day 1) post-infection and then leucocytosis at day 4 (96 h), then leucopenia at day 8 and 9. Differential leucocytes count revealed gradual neutrophilia and lymphopenia at 120 h post infection (maximum), then neutropenia and lymphocytosis at day 7 and 9. Swab cultured from liver, spleen, and lung revealed positive for P. multocida and Staphylococcus aureus. Histological sections of such organs showed abscess formation surrounded by neutrophils. In Pasteurella multocida inoculated animals (Group 2), total leucocytes count started to increase gradually at day 1 and 2, then decreased to normal level at day 3 and leucocytosis at day 4 (maximum) and then gradual decreased to reach the normal level at day 9. Differential leucocytes count revealed, neutropenia and lymphocytosis at 24 hour post infection, and remain with the same level reaching maximun at day 9 with atypical lymphocytes. Swab cultured from liver, spleen and lungs showed negative for bacterial isolation. Histological sections of such organs reveled erythrocyte infiltration and mild infiltration of inflammatory cells.