Pathogenicity and Survival of Cutibacterium Acnes in Intervertebral Discs at Different Time Points

STUDY DESIGN: An animal laboratory study. OBJECTIVE: This study aimed to investigate the pathogenicity and survival of Cutibacterium acnes ( C. acnes ) in rat intervertebral discs (IVD) across different time periods. SUMMARY OF BACKGROUND DATA: Since C. acnes was proposed as a potential causative agent of intervertebral disc degeneration (IDD), it has been the subject of widespread controversy. This study examined the removal of C. acnes from IVD, supporting the theory of its role in IDD. MATERIALS AND METHODS: Fifty rats were randomly assigned to a control group or groups with different C. acnes -causing bacterial exposure periods (4, 8, 12, and 16 wk). Except for the control group, rats in the experimental group received 5 μl of C.acnes (1×10⁷ CFU/mL) injected at L5-6. X-ray examinations, magnetic resonance imaging (MRI), fluorescence in situ hybridization (FISH) assays, tissue staining, tissue immunofluorescence (IF), and real-time polymerase chain reaction (RT-PCR) were performed. RESULTS: X-rays revealed that the C. acnes group exhibited mild narrowing of the intervertebral space four weeks postoperatively. MRI revealed that the T2-weighted signal intensity of the nucleus pulposus (NP) in the C. acnes group decreased at four weeks after operation. Histochemical staining revealed that at 4, 8, 12, and 16 weeks postinfection, the C. acnes group exhibited reduced IVD height and structural disruption of the IVD. IF results indicated a significant decrease in Aggrecan expression and a significant increase in MMP3 expression in the C. acnes group. C.acnes were cultured in IVD samples at 4, 8, and 12 weeks, while C.acnes were not cultured in IVD tissues at 16 weeks. CONCLUSION: Infection of rat IVD with C. acnes -induced IDD at all time points postinfection. Furthermore, as the duration of infection increased, C. acnes became increasingly difficult to culture from IVD tissue.