Objective: To investigate the appropriate concentration of methicillin-resistant Staphylococcus aureus (MRSA) in establishing chronic femoral osteomyelitis model in rabbits.
Methods: Forty-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 1×10 9, 1×10 8, 1×10 7, 1×10 6, 1×10 5 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.
Results: Five 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).
Conclusion: The optimal MRSA concentration of rabbit model of chronic osteomyelitis of femur is between 1×10 6 and 1×10 7 CFU/mL.
目的: 探讨采用耐甲氧西林金黄色葡萄球菌（methicillin-resistant Staphylococcus aureus，MRSA）建立兔股骨慢性骨髓炎模型的合适浓度。.
方法: 取成年新西兰大白兔 48 只随机分为 6 组，每组 8 只，B、C、D、E、F 组分别于股骨髁上 2 cm 处注射 1×10 9、1×10 8、1×10 7、1×10 6、1×10 5 CFU/mL MRSA，A 组注射无菌生理盐水作为对照。术后 4 周行实验动物大体观察，取伤口分泌物行细菌学检查；术前及术后 2、4 周检测血清 C 反应蛋白含量；术后 4 周行 X 线片及 CT 检查并行 Norden 影像学评分；术后 4 周处死动物取材后行标本大体观察及评分，并行 HE 染色观察及组织学评分。.
结果: B 组因感染严重死亡 5 只动物，C 组死亡 2 只，D、E、F 组均无动物死亡。大体观察 A 组切口愈合良好，无软组织肿胀；B～D 组大部分可见切口红肿及窦道形成，股骨增粗，骨质破坏，破坏程度随浓度降低而降低；E、F 组切口可见感染征象，感染程度不及 D 组。细菌学观察示 B、C、D、E 组切口窦道形成动物均培养出阳性结果，随着浓度降低，切口窦道形成动物数目逐渐降低；F 组无窦道形成遂未做细菌学培养。术前各组间 C 反应蛋白含量差异无统计学意义（ P>0.05）；术后 2、4 周 B～F 组 C 反应蛋白含量均显著高于 A 组（ P<0.05）；术后 4 周 C 反应蛋白含量 B 组>C 组>D 组>E 组>F 组>A 组，各组间比较差异均有统计学意义（ P<0.05）。影像学检测示 A 组无软组织肿胀及骨质破坏；B、C 组可见骨质破坏，大量死骨形成，软组织肿胀严重；D、E 组可见骨质破坏，死骨形成程度不及 C 组；F 组可见少量骨感染。B～F 组 Norden 评分显著高于 A 组，B、C 组显著高于 D、E、F 组，D、E 组显著高于 F 组（ P<0.05）；B、C 组间及 D、E 组间比较差异无统计学意义（ P>0.05）。B～F 组标本大体观察评分显著高于 A 组，B、C 组显著高于 D、E、F 组（ P<0.05）；D、E、F 组间比较差异无统计学意义（ P>0.05）。HE 染色示 A 组骨小梁结构清晰，结构排列整齐；B～F 组可见骨小梁破坏，炎性细胞浸润且程度逐渐降低。B～F 组组织学评分显著高于 A 组，B 组显著高于 C～F 组，C、D 组显著高于 F 组（ P<0.05）；C、D、E 组间以及 E、F 组间比较差异均无统计学意义（ P>0.05）。.
结论: 采用 MRSA 制备兔股骨慢性骨髓炎模型的最佳菌液浓度为 1×10 6～1×10 7 CFU/mL。.
Keywords: Chronic osteomyelitis; animal model; methicillin-resistant Staphylococcus aureus; rabbit.