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Propionibacterium acnes biofilm is present in intervertebral discs of patients undergoing microdiscectomy
Manu N Capoor1,2, Filip Ruzicka3, Jonathan E Schmitz4
1Laboratory of Bacterial Pathogenesis and Immunology, Rockefeller University, New York, New York, United States of America.
Background:
In previous studies, Propionibacterium acnes was cultured from intervertebral disc tissue of ~25% of patients undergoing microdiscectomy, suggesting a possible link between chronic bacterial infection and disc degeneration. However, given the prominence of P. acnes as a skin commensal, such analyses often struggled to exclude the alternate possibility that these organisms represent perioperative microbiologic contamination. This investigation seeks to validate P. acnes prevalence in resected disc cultures, while providing microscopic evidence of P. acnes biofilm in the intervertebral discs.
Methods:
Specimens from 368 patients undergoing microdiscectomy for disc herniation were divided into several fragments, one being homogenized, subjected to quantitative anaerobic culture, and assessed for bacterial growth, and a second fragment frozen for additional analyses. Colonies were identified by MALDI-TOF mass spectrometry and P. acnes phylotyping was conducted by multiplex PCR. For a sub-set of specimens, bacteria localization within the disc was assessed by microscopy using confocal laser scanning and FISH.
Results:
Bacteria were cultured from 162 discs (44%), including 119 cases (32.3%) with P. acnes. In 89 cases, P. acnes was cultured exclusively; in 30 cases, it was isolated in combination with other bacteria (primarily coagulase-negative Staphylococcus spp.) Among positive specimens, the median P. acnes bacterial burden was 350 CFU/g (12 - ~20,000 CFU/g). Thirty-eight P. acnes isolates were subjected to molecular sub-typing, identifying 4 of 6 defined phylogroups: IA1, IB, IC, and II. Eight culture-positive specimens were evaluated by fluorescence microscopy and revealed P. acnes in situ. Notably, these bacteria demonstrated a biofilm distribution within the disc matrix. P. acnes bacteria were more prevalent in males than females (39% vs. 23%, p = 0.0013).
Conclusions:
This study confirms that P. acnes is prevalent in herniated disc tissue. Moreover, it provides the first visual evidence of P. acnes biofilms within such specimens, consistent with infection rather than microbiologic contamination.
Insights
Propionibacterium acnes (P. acnes) is frequently found in herniated disc tissue, suggesting a role in disc degeneration. This study provides the first microscopic evidence of P. acnes biofilms, supporting an infectious cause.
Area of Science:
- Microbiology
- Orthopedic Surgery
- Spinal Degeneration
Background:
- Propionibacterium acnes (P. acnes) has been cultured from intervertebral disc tissue, but contamination is a concern.
- Previous findings suggested a link between P. acnes and disc degeneration, but lacked definitive proof against contamination.
Purpose of the Study:
- To validate the prevalence of P. acnes in herniated disc tissue.
- To provide microscopic evidence of P. acnes biofilms in intervertebral discs to distinguish infection from contamination.
Main Methods:
- Quantitative anaerobic culture of 368 microdiscectomy specimens for bacterial identification (MALDI-TOF MS).
- P. acnes phylotyping using multiplex PCR.
- Fluorescence in situ hybridization (FISH) and confocal laser scanning microscopy to visualize bacteria within disc tissue.
Main Results:
- P. acnes was cultured from 32.3% of discs, with 89 cases showing exclusive isolation.
- P. acnes bacteria were observed in situ within the disc matrix, exhibiting biofilm formation.
- P. acnes prevalence was higher in males (39%) compared to females (23%).
Conclusions:
- P. acnes is confirmed as prevalent in herniated disc tissue.
- Visual evidence of P. acnes biofilms supports an infectious etiology for disc degeneration, not contamination.