The Different Influence of Cutibacterium Acnes and Staphylococcus Epidermidis in the Lumbar Disc: An in Vivo Study in Rabbits.

Abstract

Animal laboratory study. This study investigated the effects of C. acnes and S. epidermidis on the lumbar discs of rabbits, as well as the outcomes of combined infection. Many studies have indicated that bacterial infections are associated with lumbar disc degeneration (LDD). The most commonly cultured bacteria from disc tissues are Cutibacterium acne (C. acnes) and Staphylococcus epidermidis (S. epidermidis). New Zealand white rabbits (n=40) were randomly divided into control, C. acnes, S. epidermidis, and C. acnes plus S. epidermidis (i.e., combined) groups. All groups except the control were injected with 25μL of saline at L4-L5 and 25μL of bacteria (1×107 CFU/mL) at L5-L6. All injections were performed under X-ray guidance. Weight measurements, haematological evaluations, and magnetic resonance imaging were performed after 4, 8, and 12 weeks. Histological examination and gene expression detection were performed 12 weeks after surgery. Inflammatory factors in the blood and weight did not differ among the groups after 4, 8, and 12 weeks (P >0.05). However, after 4 weeks, LDD occurred in the C. acnes group, and discitis occurred in the S. epidermidis and combined groups, all of which worsened after 8 weeks. After 12 weeks, the nucleus pulposus (NP) protruded and compressed the spinal cord in the C. acnes group, and tissue staining showed decreased NP tissue and cartilaginous endplate fracture. In the S. epidermidis and combined groups, the discitis was more confined, but tissue staining revealed a significant decrease in NP tissue, and loss of the normal disc structure. In the early stage of infection in rabbits, C. acnes caused LDD, and S. epidermidis caused discitis. Co-infection with C. acnes and S. epidermidis caused discitis but was more limited in scope than infection with S. epidermidis alone.