| Objective To study the mechanism of human β-defensin 3 (HBD-3) in methicillin-resistant Staphylococcus aureus (MRSA)-induced infection of implant drug-resistant bacteria biofilm in the rat tibial bone marrow. Methods The SD rats were selected to construct the model of MRSA-induced implant biofilm infection in the left tibial bone marrow. The drugs were intraperitoneally injected after 24 h medullary cavity infection, and the experimental groups included the model group, HBD-3 group, and vancomycin group (20 rats in each group). The model group was injected with 2 mL saline, HBD-3 group was injected with 2 mL 8 μg/ml (1MIC) HBD-3 and vancomycin group was injected with 2 mL 0.5μg/mL (1 MIC) vancomycin. Five animals that had been injected in each group were sacrificed on the 1st, 7th, 14th, and 21st day, respectively. The laser scanning confocal microscopy was used to observe the morphology of the biofilm and the number of viable bacteria. Immunohistochemical staining was adopted to test the expressions of NF-κB and TLR-4, and ELISA was used to test IL-10 and TNF-α expression levels. Results The percentage of the neutrophile granulocytes, total white blood cells and the number of viable bacteria in the model group was gradually increased, while those in the HBD-3 and vancomycin groups were decreased gradually (P< 0.05). The NF-κB and TLR-4 expressions in the HBD-3 group began to increase on the 1st day, reached the peak on the 7th day and began to be fallen on the 14th day; those in the HBD-3 group were significantly higher than the model group and vancomycin group at each time point (P< 0.05). The IL-10 and TNF-α expressions in the model group at each time were significantly higher than the other two groups (P<0.05). Conclusion HBD-3 can inhibit the bacterial growth by regulating inflammations and immune responses in the MRSA-induced implant biofilm infection in the rat tibial bone marrow. |
