Histological Identification of Propionibacterium acnes in Nonpyogenic Degenerated Intervertebral Discs

Purpose. Low-virulence anaerobic bacteria, especially the Propionibacterium acnes (P. acnes), have been thought to be a new pathogeny for a series of disc diseases. However, until now, there has been no histological evidence to confirm this link. The purpose of this study was to confirm the presence of P. acnes in nonpyogenic intervertebral discs via histological observation. Method. Degenerated intervertebral discs were harvested from 76 patients with low back pain and/or sciatica but without any symptoms of discitis or spondylodiscitis. The samples were cultured under anaerobic conditions and then examined using 16S rDNA PCR to screen for P. acnes. Samples found to be positive for P. acnes were stained with hematoxylin-eosin (HE) and modified Brown-Brenn staining and observed under a microscope. Results. Here, 16 intervertebral discs were found to be positive for P. acnes via 16S rDNA PCR and the prevalence was 21.05% (16/76). Among them, 7 samples had visible microbes stained with HE and modified Brown-Brenn staining. Morphological examination showed the bacteria to be Gram-positive and rod-shaped, so they were considered P. acnes. Conclusion. P. acnes is capable of colonizing some degenerated intervertebral discs without causing discitis, and its presence could be further confirmed by histological evidence. Targeting these bacteria may be a promising therapy method for some disc diseases.