【Animal Modeling】-Preparation of a mouse model of methicillin-resistant Staphylococcus aureus systemic infection

  Objective: To infect ICR mice with clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) and establish a mouse model of systemic MRSA infection.

  Method: Cyclophosphamide (100 mg/kg) was injected intraperitoneally for 3 consecutive days for immunosuppression, and then the MRSA bacterial solution with a concentration of 1×107 cfu/mL was injected into ICR mice through the tail vein to survive. Perform tissue load and pathological examination to analyze and evaluate peripheral blood leukocyte models.

  Result: Two days after MRSA vaccination, mice began to die, and within 14 days, the cumulative mortality rate reached 60%, the total number of white blood cells in peripheral blood increased significantly, and bacteria colonized multiple organs. The bacterial load is in descending order: the highest content in kidney, joint, lung, liver, brain, kidney is 109 CFU/g, and the highest content in joint, lung, liver, and brain is 104-109 CFU/g. Pathological observation showed histopathological changes of multiple organ infections in kidney, heart, lung, liver, brain and joints.

  Conclusion: Intravenous MRSA after cyclophosphamide immunosuppression is the first successful method to establish a mouse model of systemic MRSA infection.