Validation of the Osteomyelitis Induced by Methicillin-Resistant Staphylococcus aureus (MRSA) on Rat Model with Calvaria Defect

Background: Osteomyelitis resulting from bacterial strains, such as methicillin-resistant Staphylococcus aureus (MRSA) that are resistant to multiple drugs, brings further clinical challenges. There is currently no model of osteomyelitis induced by MRSA using rats with calvaria defects. So, We induced osteomyelitis in rat models with the calvaria bone defect. Methods: The rats were randomly divided into six groups according to inoculation dose levels, which ranged from 6 x 10(0) to 6 x 10(5) CFU/5 mu l. Bone tissues were retrieved from all rats used in the study and assessed using histology, microbiology, and radiobiology 4 weeks after surgery to evaluate the relationship between inoculation dose and infectivity. Results: In Histological results, high levels of inflammatory responses, bone necrosis, and bacteria were observed in treatment groups G3 to G5. In IHC staining, high levels of cox-2 expression were observed in treatment groups G3. Microbiological observations also indicated that significantly higher numbers of CFUs were found in G3 to G5. In radiography results, the bone mineral density in G3 to G5 was significantly higher than in the control group, G1, and G2. Our results indicate that an inoculating dose of 6 x 10(3) CFU/5 mu l is sufficient to induce the development of osteomyelitis in rat models. Conclusion: This study suggests that the minimum dose (6 x 10(3) CFU/5 mu l) can induce osteomyelitis in calvaria rat model. This can offer information and ability of more accurately modeling osteomyelitis and simulating the challenge of osteomyelitis treat.