ObjectiveTo investigate the appropriate concentration of methicillin-resistant Staphylococcus aureus (MRSA) in establishing chronic femoral osteomyelitis model in rabbits.MethodsForty-eight adult New Zealand white rabbits were randomly divided into 6 groups with 8 rabbits in each group. Animals in groups B, C, D, E, and F were injected 1×10⁹, 1×10⁸, 1×10⁷, 1×10⁶, 1×10⁵ CFU/mL MRSA on the location of 2 cm of the femoral supracondyle, respectively, and group A was injected with aseptic saline as a control. The general observation were performed at 4 weeks after operation, and the wound secretions were taken for bacteriological examination. The serum C-reactive protein content was detected at preoperation and 2 weeks and 4 weeks after operation. The X-ray, CT scan, and Norden imaging scoring were performed at 4 weeks after operation. At 4 weeks after operation, the animals were sacrificed, and the specimens were observed and evaluated by general scores; and the HE staining and histological score were also performed.ResultsFive rabbits died of severe infection in group B, 2 died in group C, and no rabbit died in groups D, E, and F. General observation showed that the incision healed without soft tissue swelling in group A; most animals had visible incision swelling and sinus formation, femoral thickening, bone destruction, and damage decreased with the decreasing of the concentration of liquid bacterial in groups B-D; the infection signs were seen in groups E and F, and the degree of infection were less than that of group D. Bacteriological examination showed that fistula formation animal in groups B, C, D, and E were cultured with positive results, and with the decrease of concentration, the number of animal fistula formation decreased gradually; and bacteriological culture did not be performed in group F because of no sinus formation. There was no significant difference in the content of C-reactive protein between groups before operation (P>0.05). The contents of C-reactive protein in groups B-F were significantly higher than those in group A at 2 and 4 weeks after operation (P<0.05). At 4 weeks after operation, the content of C-reactive protein was in the order of groups B, C, D, E, F, and A in turn from high to low, showing significant differences between groups (P<0.05). Imaging examination showed that there was no soft tissue swelling and bone destruction in group A; bone destruction, massive sequestrum formation, and soft tissue swelling were found in groups B and C; bone destruction was observed in groups D and E, and the degree of sequestrum formation was not as good as that in group C; and there was a small amount of bone infection in group F. The Norden scores in groups B-F were significantly higher than that in group A, and in groups B and C than those in groups D, E, and F, and in groups D and E than that in group F (P<0.05); there was no significant difference between groups B and C, and between groups D and E (P>0.05). The specimens general observation scores in groups B-F were significantly higher than that in group A, while in groups B and C than those in groups D, E, and F (P<0.05); there was no significant difference between groups D, E, and F (P>0.05). HE staining showed that the structure of bone trabecula in group A was clear and the structure was arranged neatly; in groups B-F, trabecular bone destruction and inflammatory cell infiltration were seen and the degree gradually decreased. The histological scores in groups B-F were significantly higher than that in group A, and in group B than those in groups C-F, in groups C and D than that in group F (P<0.05); there was no significant difference between groups C, D, and E, and between groups E and F (P>0.05).ConclusionThe optimal MRSA concentration of rabbit model of chronic osteomyelitis of femur is between 1×10⁶ and 1×10⁷ CFU/mL.

Citation： SHAO Longlong, ZHEN Ping, MA Yonghai, GONG Dong, WANG Yunlong. Comparative study of different concentrations of methicillin-resistant Staphylococcus aureus in the preparation of chronic femoral osteomyelitis models . Chinese Journal of Reparative and Reconstructive Surgery, 2018, 32(4): 412-419. doi: 10.7507/1002-1892.201711082 Copy