Prevalence of Propionibacterium acnes in Intervertebral Discs of Patients Undergoing Lumbar Microdiscectomy: A Prospective Cross-Sectional Study

Intervertebral disc microbiome in Modic changes: Lack of result replication underscores the need for a consensus in low-biomass microbiome analysis

Introduction

The emerging field of the disc microbiome challenges traditional views of disc sterility, which opens new avenues for novel clinical insights. However, the lack of methodological consensus in disc microbiome studies introduces discrepancies. The aims of this study were to (1) compare the disc microbiome of non-Modic (nonMC), Modic type 1 change (MC1), and MC2 discs to findings from prior disc microbiome studies, and (2) investigate if discrepancies to prior studies can be explained with bioinformatic variations.

Methods

Sequencing of 16S rRNA in 70 discs (24 nonMC, 25 MC1, and 21 MC2) for microbiome profiling. The experimental setup included buffer contamination controls and was performed under aseptic conditions. Methodology and results were contrasted with previous disc microbiome studies. Critical bioinformatic steps that were different in our best-practice approach and previous disc microbiome studies (taxonomic lineage assignment, prevalence cut-off) were varied and their effect on results were compared.

Results

There was limited overlap of results with a previous study on MC disc microbiome. No bacterial genera were shared using the same bioinformatic parameters. Taxonomic lineage assignment using "amplicon sequencing variants" was more sensitive and detected 48 genera compared to 22 with "operational taxonomic units" (previous study). Increasing filter cut-off from 4% to 50% (previous study) reduced genera from 48 to 4 genera. Despite these differences, both studies observed dysbiosis with an increased abundance of gram-negative bacteria in MC discs as well as a lower beta-diversity. Cutibacterium was persistently detected in all groups independent of the bioinformatic approach, emphasizing its prevalence.

Conclusion

There is dysbiosis in MC discs. Bioinformatic parameters impact results yet cannot explain the different findings from this and a previous study. Therefore, discrepancies are likely caused by different sample preparations or true biologic differences. Harmonized protocols are required to advance understanding of the disc microbiome and its clinical implications.

Risk factors associated with low-grade virulent infection in intervertebral disc degeneration: a systematic review and meta-analysis

BACKGROUND

An increasing number of research indicates an association between low-grade bacterial infections, particularly those caused by Propionibacterium acnes (P. acnes), and the development of intervertebral disc degeneration (IDD). However, no previous meta-analysis has systematically assessed the risk factors for low-grade bacterial infections that cause IDD.

PURPOSE

This study reviewed the literature to evaluate the risk factors associated with low-grade bacterial infection in patients with IDD.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

The systematic literature review was conducted using the PubMed, Web of Science, Embase, and Cochrane Library databases. Eligible articles explicitly identified the risk factors for low-grade bacterial infections in IDD patients. Patient demographics and total bacterial infection rates were extracted from each study. Meta-analysis was performed using random- or fixed-effects models, with statistical analyses conducted using Review Manager (RevMan) 5.4 software.aut.

RESULTS

Thirty-three studies involving 4,109 patients were included in the meta-analysis. The overall pooled low-grade bacterial infection rate was 30% (range, 24%-37%), with P. acnes accounting for 25% (range, 19%-31%). P. acnes constituted 66.7% of bacteria-positive discs. Fourteen risk factors were identified, of which 8 were quantitatively explored. Strong evidence supported male sex (odds ratio [OR] = 2.15; 95% confidence interval [CI]=1.65-2.79; p<.00001) and Modic changes (MCs) (OR=3.59; 95% CI=1.68-7.76; p=.0009); moderate evidence of sciatica (OR=2.31; 95% CI=1.33-4.00; p=.003) and younger age (OR=-3.47; 95% CI=-6.42 to -0.53; p=.02). No evidence supported previous disc surgery, MC type, Pfirrmann grade, smoking, or diabetes being risk factors for low-grade bacterial infections in patients with IDD.

CONCLUSIONS

Current evidence highlights a significant association between IDD and low-grade bacterial infections, predominantly P. acnes being the most common causative agent. Risk factors associated with low-grade bacterial infections in IDD include male sex, MCs, sciatica, and younger age.

Cutibacterium acnes in spine surgery: pathophysiology, diagnosis, and treatment

Cutibacterium acnes (C. acnes) previously named Propionibacterium acnes (P. acnes) has been increasingly recognized by spine surgeons as a cause of indolent post-surgical spinal infection. Patients infected with C. acnes may present with pseudarthrosis or nonspecific back pain. Currently, microbiological tissue cultures remain the gold standard in diagnosing C. acnes infection. Ongoing research into using genetic sequencing as a diagnostic method shows promising results and may be another future way of diagnosis. Optimized prophylaxis involves the use of targeted antibiotics, longer duration of antibiotic prophylaxis, antibacterial-coated spinal implants, and evidence-based sterile surgical techniques all of which decrease contamination. Antibiotics and implant replacement remain the mainstay of treatment, with longer durations of antibiotics proving to be more efficacious. Local guidelines must consider the surge of antimicrobial resistance worldwide when treating C. acnes.

Achilles' Heel-The Significance of Maintaining Microenvironmental Homeostasis in the Nucleus Pulposus for Intervertebral Discs

The dysregulation of intracellular and extracellular environments as well as the aberrant expression of ion channels on the cell membrane are intricately linked to a diverse array of degenerative disorders, including intervertebral disc degeneration. This condition is a significant contributor to low back pain, which poses a substantial burden on both personal quality of life and societal economics. Changes in the number and function of ion channels can disrupt the water and ion balance both inside and outside cells, thereby impacting the physiological functions of tissues and organs. Therefore, maintaining ion homeostasis and stable expression of ion channels within the cellular microenvironment may prove beneficial in the treatment of disc degeneration. Aquaporin (AQP), calcium ion channels, and acid-sensitive ion channels (ASIC) play crucial roles in regulating water, calcium ions, and hydrogen ions levels. These channels have significant effects on physiological and pathological processes such as cellular aging, inflammatory response, stromal decomposition, endoplasmic reticulum stress, and accumulation of cell metabolites. Additionally, Piezo 1, transient receptor potential vanilloid type 4 (TRPV4), tension response enhancer binding protein (TonEBP), potassium ions, zinc ions, and tungsten all play a role in the process of intervertebral disc degeneration. This review endeavors to elucidate alterations in the microenvironment of the nucleus pulposus during intervertebral disc degeneration (IVDD), with a view to offer novel insights and approaches for exploring therapeutic interventions against disc degeneration.

The association between low virulence organisms in different locations and intervertebral disc structural failure: A meta-analysis and systematic review

Many factors may trigger intervertebral disc (IVD) structural failure (intervertebral disc degeneration (IDD) and endplate changes), including inflammation, infection, dysbiosis, and the downstream effects of chemical factors. Of these, microbial diversity in the IVD and elsewhere in the body has been considered as one of the potential reasons for disc structural failure. The exact relationships between microbial colonization and IVD structural failure are not well understood. This meta-analysis aimed to investigate the impact of microbial colonization and its location (such as skin, IVD, muscle, soft tissues, and blood) on IVD structural failure and corresponding low back pain (LBP) if any. We searched four online databases for potential studies. The potential relationships between microbial colonization in different sample sources (such as skin, IVD, muscle, soft tissues, and blood) and IDD and endplate change were considered as primary outcomes. Odds ratio (OR) and 95% confidence intervals (CI) for direct comparisons were reported. Grading of Recommendations Assessment, Development and Evaluation (GRADE) scale was used to assess the quality of evidence. Twenty-five cohort studies met the selection criteria. Overall pooled prevalence of microbial colonization in 2419 patients with LBP was 33.2% (23.6%-43.6%). The pooled prevalence of microbial colonization in 2901 samples was 29.6% (21.0%-38.9%). Compared with the patients without endplate change, the patients with endplate changes had higher rates of microbial colonization of disc (OR = 2.83; 95% CI = 1.93-4.14; I ² = 37.6%; p = 0.108). The primary pathogen was Cutibacterium acnes which was present in 22.2% of cases (95% CI = 13.3%-32.5%; I ² = 96.6%; p = 0.000). This meta-analysis and systematic review found low-quality grade evidence for an association between microbial colonization of disc with endplate changes. The primary pathogen was C. acnes. Due to lack of enough high-quality studies and methodological limitations of this review, further studies are required to improve our understanding of the potential relationships and mechanisms of microbiota, dysbiosis, IVD colonization and IVD structural failure.

Cytokine Patterns as Predictors of Antibiotic Treatment Effect in Chronic Low Back Pain with Modic Changes: Subgroup Analyses of a Randomized Trial (AIM Study)

Objective

Randomized trials testing the effect of antibiotics for chronic low back pain (LBP) with vertebral bone marrow changes on MRI (Modic changes) report inconsistent results. A proposed explanation is subgroups with low grade discitis where antibiotics are effective, but there is currently no method to identify such subgroups. The objective of the present study was to evaluate whether distinct patterns of serum cytokine levels predict any treatment effect of oral amoxicillin at one-year follow-up in patients with chronic low back pain and Modic changes at the level of a previous lumbar disc herniation.

Design

We used data from an overpowered, randomized, placebo-controlled trial (the AIM study) that tested 100 days of oral 750 mg amoxicillin vs placebo three times daily in hospital outpatients with chronic (>6 months) LBP with pain intensity ≥5 on a 0-10 numerical rating scale and Modic changes type 1 (oedema type) or 2 (fatty type). We measured serum levels of 40 inflammatory cytokines at baseline and analysed six predefined potential predictors of treatment effect based on cytokine patterns in 78 randomized patients; three analyses with recursive partitioning, one based on cluster analysis and two based on principal component analyses. The primary outcome was the Roland-Morris Disability Questionnaire score at one-year follow-up in the intention to treat population. The methodology and overall results of the AIM study were published previously.

Results

The 78 patients were 25-62 years old and 47 (60%) were women. None of the three recursive partitioning analyses resulted in any suggested subgroups. Of all main analyses, the largest effect estimate (mean difference between antibiotic and placebo groups) was seen in a subgroup not predefined as of main interest (Cluster category 3+4; -2.0, 95% CI: -5.2-1.3, RMDQ points; p-value for interaction 0.54).

Conclusion

Patterns of inflammatory serum cytokine levels did not predict treatment effect of amoxicillin in patients with chronic LBP and Modic changes.

Clinical Trial Registration Number

ClinicalTrials.gov (identifier: NCT02323412).

Would Cutibacterium acnes Be the Villain for the Chronicity of Low Back Pain in Degenerative Disc Disease? Preliminary Results of an Analytical Cohort

In the last decade, several studies have demonstrated Cutibacterium acnes colonization in intervertebral discs (IVDs) in patients with lumbar disc degeneration (LDD) and low back pain (LBP), but the meaning of these findings remains unclear. Being aware of this knowledge gap, we are currently conducting a prospective analytical cohort study with LBP and LDD patients undergoing lumbar microdiscectomy and posterior fusion. The IVDs samples collected during the surgeries are subjected to a stringent analytical protocol using microbiological, phenotypic, genotypic, and multiomic techniques. Additionally, pain-related scores and quality-of-life indexes are monitored during patient follow-up. Our preliminary results for 265 samples (53 discs from 23 patients) revealed a C. acnes prevalence of 34.8%, among which the phylotypes IB and II were the most commonly isolated. The incidence of neuropathic pain was significantly higher in the colonized patients, especially between the third and sixth postoperative months, which strongly suggests that the pathogen plays an important role in the chronicity of LBP. The future results of our protocol will help us to understand how C. acnes contributes to transforming inflammatory/nociceptive pain into neuropathic pain and, hopefully, will help us to find a biomarker capable of predicting the risk of chronic LBP in this scenario.

Evaluating Nonoperative Treatment for Low Back Pain in the Presence of Modic Changes: A Systematic Review

OBJECTIVE

The objective of this study was to summarize and assess the current literature evaluating nonoperative treatments for patients with Modic changes (MCs) and low back pain (LBP).

METHODS

A systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The PubMed database was searched from its inception until May 1, 2022 for studies evaluating MC and clinical outcomes. Key findings, treatment details, and patient information were extracted from included studies. Study quality was assessed using the Newcastle-Ottawa Scale.

RESULTS

Eighteen studies were included in this review, encompassing a total of 2452 patients, 1713 of whom displayed baseline MC. Seventy-eight percent of studies were high quality. Of included studies, 2 evaluated antibiotics, 5 evaluated steroid injections, 6 evaluated conservative therapies, and 5 evaluated other treatment modalities. Antibiotics and bisphosphonates improved treatment in patients with MC. Patients with MC without disc herniation benefited from conservative therapy, while those with Type I Modic changes and disc herniation experienced poorer improvement. Significant variability exists in reported outcomes following steroid injections.

CONCLUSIONS

Nonoperative therapy may provide patients with MC with significant benefits. Patients may benefit from therapies not traditionally utilized for LBP such as antibiotics or bisphosphonates, but conservative therapy is not recommended for patients with concomitant MC and disc herniation. The large variation in follow-up times and outcome measures contributes to significant heterogeneity in studies and inability to predict long-term patient outcomes. More long-term studies are needed to assess nonoperative treatments for LBP in patients with MC.

Colonization of intervertebral discs by Cutibacterium acnes in patients with low back pain: Protocol for an analytical study with microbiological, phenotypic, genotypic, and multiomic techniques

Lumbar disc degeneration (LDD) and low back pain (LBP) are two conditions that are closely related. Several studies have shown Cutibacterium acnes colonization of degenerated discs, but whether and how these finding correlates with LBP is unknown. A prospective study was planned to identify molecules present in lumbar intervertebral discs (LLIVD) colonized by C. acnes in patients with LDD and LBP and correlate them with their clinical, radiological, and demographic profiles. The clinical manifestations, risk factors, and demographic characteristics of participants undergoing surgical microdiscectomy will be tracked. Samples will be isolated and pathogens found in LLIVD will be characterized phenotypically and genotypically. Whole genome sequencing (WGS) of isolated species will be used to phylotype and detect genes associated with virulence, resistance, and oxidative stress. Multiomic analyses of LLIVD colonized and non-colonized will be carried out to explain not only the pathogen's role in LDD, but also its involvement in the pathophysiology of LBP. This study was approved by the Institutional Review Board (CAAE 50077521.0.0000.5258). All patients who agree to participate in the study will sign an informed consent form. Regardless of the study's findings, the results will be published in a peer-reviewed medical journal. Trials registration number NCT05090553; pre-results.

Clinical Biomarker of Sterile Inflammation, HMGB1, in Patients with Chronic Non-Specific Low Back Pain: A Pilot Cross-Sectional Study

The present study explores whether the inflammatory biomarker of sterile inflammation, high mobility box 1 (HMGB1), contributes to the inflammatory/nociceptive pathophysiology that characterizes chronic non-specific low back pain (LBP). Patients with chronic LBP (N = 10, >3 pain score on a 11-point Visual Analogue Scale, VAS) and asymptomatic participants (N = 12) provided peripheral blood (PB) samples. The proportion of classical CD14++ monocytes within PB leukocytes was determined by flow cytometry. The plasma and extracellular HMGB1 levels in unstimulated adherent cell (AC) cultures were measured using specific immunoassays. HMGB1 localization in ACs was assessed by immunofluorescent staining. The relative gene expression levels of tumor necrosis factor α (TNFα), interleukin-1 beta (IL-1β) and HMGB1 were determined by quantitative polymerase chain reaction (qRT-PCR) in relation to the pain intensity (11-point VAS scores) in patients with LBP. The extracellular release of HMGB1 in the LBP patient AC cultures was significantly elevated (p = 0.001) and accompanied by its relocation into the cytoplasm from the nuclei. The number of CD14++ monocytes in the patients' PB was significantly (p = 0.03) reduced, while the HMGB1 plasma levels remained comparable to those of the controls. The mRNA levels of TNFα, IL-1β and HMGB1 were overexpressed relative to the controls and those of HMGB1 and IL-1β were correlated with the VAS scores at a significant level (p = 0.01-0.03). The results suggest that HMGB1 may play an important role in the pathophysiology of chronic non-specific LBP.

Are Modic changes 'Primary infective endplatitis'?-insights from multimodal imaging of non-specific low back pain patients and development of a radiological 'Endplate infection probability score'

PURPOSE

To probe the pathophysiological basis of Modic change (MC) by multimodal imaging rather than by MRI alone.

METHODS

Nineteen radiological signs found in mild infections and traumatic endplate fractures were identified by MRI and CT, and by elimination, three signs unique to infection and trauma were distilled. By ranking the Z score, radiological 'Endplate Infection Probability Score' (EIPS) was developed. The score's ability to differentiate infection and traumatic endplate changes (EPC) was validated in a fresh set of 15 patients each, with documented infection and trauma. The EIPS, ESR, CRP, and Numeric Pain Rating Scale (NRS) were then compared between 115 patients with and 80 patients without MC.

RESULTS

The EIPS had a confidence of 66.4%, 83% and, 100% for scores of 4, 5 and, 6, respectively, for end plate changes suggesting infection. The mean EIPS was 4.85 ± 1.94 in patients with Modic changes compared to - 0.66 ± 0.49 in patients without Modic changes (p < 0.001). Seventy-eight (67.64%) patients with MC had a score of 6, indicating high infection possibility. There was a difference in the NRS (p < 0.01), ESR (p = 0.05), CRP (p < 0.01), and type of pain (p < 0.01) between patients with and without MC.

CONCLUSION

Multimodal imaging showed many radiological signs not easily seen in MRI alone and thus missed in Modic classification. There were distinct radiological differences between EPCs of trauma and infection which allowed the development of an EIPS. The scores showed that 67.64% of our study patients with Modic changes had EPCs resembling infection rather than trauma suggesting the possibility of an infective aetiology and allowing us to propose an alternate theory of 'Primary Endplatitis'.

Different phylotypes of Cutibacterium acnes cause different modic changes in intervertebral disc degeneration

Background

The contribution of Cutibacterium acnes (C. acnes) infection to intervertebral disc degeneration (IDD) and the antibiotic therapy has evoked several controversies in recent years. While some microbiology studies report bacterial disc infection within IDD patients, others attribute the positive results to contamination during prolonged cultures. In addition to the clinical controversy, little was known about the mechanism of C. acnes-caused Modic changes (MCs) if C. acnes was the pathogenic factor.

Objectives

This study aimed to investigate the inflammatory mechanism of MCs induced by different phylotypes of C. acnes in patients with IDD.

Methods

Specimens from sixty patients undergoing microdiscectomy for disc herniation were included, C. acnes were identified by anaerobic culture, followed by biochemical and PCR-based methods. The identified species of C. acnes were respectively inoculated into the intervertebral discs of rabbits. MRI and histological change were observed. Additionally, we detected MMP expression in the rabbit model using reverse transcription-quantitative polymerase chain reaction (RT-qPCR).

Results

Of the 60 cases, 18 (30%) specimens were positive for C. acnes, and we identified 4 of 6 defined phylogroups: IA, IB, II and III. The rabbits that received Type IB or II strains of C. acnes showed significantly decreased T1WI and higher T2WI at eighth weeks, while strain III C. acnes resulted in hypointense signals on both T1WI and T2WI. Histological examination results showed that all of the three types of C. acnes could cause disc degeneration and endplates rupture. Moreover, endplate degeneration induced by type IB or II strains of C. acnes is related with MMP13 expression. Meanwhile, strain III C. acnes might upregulated the level of MMP3.

Conclusion

This study suggested that C. acnes is widespread in herniated disc tissues. Different types of C. acnes could induce different MCs by increasing MMP expression.

The Presence of Biofilms in Instrumented Spinal Fusions

Study Design: Prospective observational cohort study. Objective: To determine whether biofilms exist on spinal instrumentation recovered during revision surgery in which microbial cultures were negative. Background: Biofilm bacteria are extremely difficult to detect by conventional culture methods used in the standard hospital setting. Chronic infections in which bacteria form biofilms have been demonstrated to slow healing and prevent bony fusion. These slime encased microbial communities serve to isolate the bacteria from the body's immune responses, while simultaneously providing metabolic resistance to antimicrobial therapy. Methods: Traditional debridement wound cultures were taken from each specimen and sent for microbiological analyses. Bacterial DNA testing was performed using polymerase chain reaction (PCR) electrospray ionization-mass spectrometry (ESI-MS). Based on the PCR/ESI-MS results, specific crossed immune electrophoresis was used to detect the bacterial species within biofilms observed on the removed instrumentation. In addition, fluorescent in situ hybridization (FISH) probes corresponding to the bacterial species identified by PCR/ESI-MS were used with confocal microscopy to visualize and confirm the infecting bacteria. Results: Fifteen patients presented for surgical revision of thoracolumbar spinal implantation: four for clinical suspicion of infection, six for adjacent segment disease (ASD), one with ASD and pseudoarthrosis (PA), three with PA, and one for pain. Infections were confirmed with PCR/ESI-MS for all four patients who presented with clinical infection, and for five of the patients for whom infection was not clinically suspected. Of the presumed non-infected implants, 50% demonstrated the presence of infectious biofilms. Half of the revisions due to pseudoarthrosis were shown to harbour biofilms. The revisions that were performed for pain demonstrated robust biofilms but did not grow bacteria on traditional culture media. Conclusions: Culture is inadequate as a diagnostic modality to detect indolent/subclinical biofilm infections of spinal instrumentation. The PCR/ESI-MS results for bacterial detection were confirmed using species-specific microscopic techniques for both bacterial nucleic acids and antigens. Biofilms may contribute to pseudoarthrosis and back pain in postoperative wounds otherwise considered sterile.

MECHANISM OF MIR-25-3P CARRIED BY EXTRACELLULAR VESICLES DERIVED FROM PLATELET-RICH PLASMA IN IL-1β-INDUCED NUCLEUS PULPOSUS CELL DEGENERATION VIA THE SOX4/CXCR7 AXIS

ABSTRACT

Objectives: Nucleus pulposus (NP) cell degeneration promotes the progression of intervertebral disc (IVD) degeneration. MicroRNAs (miRs) are associated with IVD degeneration. This study expounded the mechanism of microRNA (miR)-25-3p carried by extracellular vesicles (EVs) derived from platelet-rich plasma (PRP) in interleukin (IL)-1β-induced NP cell degeneration. Methods: Platelet-rich plasma from mouse blood was obtained, and EVs were isolated from PRP (EVs derived from PRP [PRP-EVs]) and identified. Nucleus pulposus cells were isolated from the mouse lumbar IVD and treated with IL-1β to induce NP cell degeneration. Extracellular vesicles derived from PRP were added into NP cell culture medium. Afterward, intracellular miR-25-3p, sex determining region Y-related high-mobility-group box 4 (SOX4), and CXC chemokine receptor 7 (CXCR7) levels were examined. Nucleus pulposus cell viability, apoptosis, and inflammation were detected. Extracellular vesicles derived from PRP were labeled by PKH67 to obverse the uptake of EVs by NP cells. The binding relations between SOX4 and miR-25-3p and CXCR7 were predicted and examined. Functional rescue experiments were performed to investigate the roles of miR-25-3p, SOX4, and CXCR7 in NP cell degeneration. Results: miR-25-3p was downregulated, whereas SOX4 and CXCR7 were upregulated in IL-1β-induced NP cells. Extracellular vesicles derived from PRP increased the cell viability, and decreased apoptosis and inflammation. miR-25-3p carried by PRP-EVs into NP cells alleviated NP cell degeneration. miR-25-3p inhibited SOX4 expression and limited CXCR7 transcription. Silencing miR-25-3p or overexpressing SOX4 or CXCR7 reversed the alleviating role of PRP-EVs in NP cell degeneration. Conclusion: miR-25-3p carried by PRP-EVs into NP cells elevated intracellular miR-25-3p expression, which suppressed SOX4 expression and further limited CXCR7 transcription, thus alleviating IL-1β-induced NP cell degeneration. Extracellular vesicles derived from PRP containing miR-25-3p may be a new method for IVD treatment.

Frequency and characteristics of bacterial and viral low-grade infections of the intervertebral discs: a prospective, observational study

Study design

Monocentric, prospective, observational study.

Objective

The clinical relevance of bacterial colonization of intervertebral discs is controversial. This study aimed to determine a possible relationship between bacterial and viral colonization and low-grade infection of the discs.

Methods

We investigated 447 disc samples from 392 patients. Microbiological culture was used to examine the samples for bacterial growth, polymerase chain reaction (PCR) was used for detection of herpes simplex virus types 1 and 2 (HSV-1, HSV-2) and Cytomegalovirus (CMV), and histopathological analysis was used to detect signs of inflammation. The results were compared between subgroups organized according to gender, age, location of the samples, surgical approach, preoperative C-reactive protein (CRP), preoperative and 6 months postoperative Oswestry Disability Index (ODI) and Neck Disability Index (NDI), and Modic changes (MC) of the corresponding endplates. Also, we assessed the occurrence of postoperative infections within 6 months.

Results

Microbiological culture was positive in 38.78% of the analyzed intervertebral discs. Altogether, 180 bacteria were isolated. Coagulase-negative staphylococci (CONS) (23.41%) and Cutibacterium acnes (18.05%) were the most frequently detected microorganisms. None of HSV-1, HSV-2, or CMV were detected. Male patients (p = 0.00036) and cervical segments (p = 0.00001) showed higher rates of positive culture results. Ventral surgical approaches ( p < 0.001) and Type 2 MC (p = 0.0127) were significantly associated with a positive microbiological result ( p< 0.001). Neither pre- nor postoperative ODI and NDI are associated with positive culture results. In 4 (1.02%) patients, postoperative spondylodiscitis occurred.

Conclusions

With 447 segments from 392 patients, we present one of the largest studies to date. While disc degeneration caused by HSV-1, HSV-2, and CMV seems unlikely, we found positive microbiological culture results in 38.78% of all discs. The role of local skin flora and sample contamination should be the focus of further investigations.

Level of Evidence

III.

Trial registration: The study was registered at ClinicalTrials.gov (ID: NCT04712487, https://www.clinicaltrials.gov/ct2/show/study/NCT04712487).

Supplementary Information

The online version contains supplementary material available at 10.1186/s10195-022-00633-y.

Personalized multitarget biologic injection in the spine: prospective case series of multitarget platelet-rich plasma for low back pain

Aim: To evaluate the use of a multitarget platelet-rich plasma (PRP) injection approach for the treatment of chronic low back pain (LBP). Materials & Methods: Forty-six patients with more than 12 weeks of LBP who failed conservative treatments were injected with PRP into the facet joints, intervertebral discs, epidural space and/or paravertebral muscles. Visual analog pain scale and Roland-Morris Disability Questionnaire scores were measured at baseline and predefined intervals. Results: Mean visual analog pain scale was reduced from 8.48 to 5.17 and mean Roland-Morris Disability Questionnaire from 18.0 to 10.98 at 12 weeks (p < 0.001). These statistically significant improvements were sustained over 52 weeks. No adverse effects were observed. Conclusion: Our PRP approach demonstrated clinically favorable results and may be a promising treatment for chronic LBP.

Evidence for infection in intervertebral disc degeneration: a systematic review

Purpose

Back pain is a major problem worldwide and is linked to intervertebral disc degeneration and Modic change. Several studies report growth of bacteria following extraction of degenerate discs at spine surgery. A pathophysiological role for infection in back pain has been proposed.

Method

We conducted a PRISMA systematic review. MEDLINE, PubMed, Scopus and Web of Science were searched with the terms Modic change, intervertebral dis*, bacteria, microb*, and infect*. Date limits of 2001–2021 were set. Human studies investigating the role of bacteria in disc degeneration or Modic change in vertebrae were included.

Results

Thirty-six articles from 34 research investigations relating to bacteria in human degenerate discs were found. Cutibacterium acnes was identified in pathological disc material. A ‘candidate bacterium’ approach has been repeatedly adopted which may have biased results to find species a priori, with disc microbial evidence heavily weighted to find C. acnes.

Conclusion

Evidence to date implicates C. acnes identified through culture, microscopy and sequencing, with some suggestion of diverse bacterial colonisation in the disc. This review found studies which used culture methods and conventional PCR for bacterial detection.

Further agnostic investigation using newer methods should be undertaken.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00586-021-07062-1.

Clinicoradiographic predictors of percutaneous bone biopsy results among patients with suspected thoracolumbar spine infection

BACKGROUND

Image-guided percutaneous thoracolumbar spine biopsy is frequently performed in the setting of suspected septic facet arthritis or discitis osteomyelitis (DOM). There are limited data regarding factors associated with a positive biopsy result among these patients.

MATERIALS AND METHODS

Patients with suspected DOM who underwent spine biopsy were identified. Samples yielding a positive culture and/or histopathology suggestive of acute osteomyelitis were considered positive. The associations between selected medical comorbidities, laboratory values, pre-biopsy antibiotic administration, imaging findings and biopsy results were investigated.

RESULTS

121 patients underwent percutaneous biopsy with 35.5% yielding positive results. Biopsy results showed no correlation with comorbidities. The only laboratory value that correlated with a positive biopsy yield was blood culture positivity (p = 0.03). The imaging findings that correlated with a positive biopsy yield were the presence of a paraspinal fluid collection or epidural abscess (p = 0.003 and 0.018, respectively). Sampling paraspinal fluid collections, when present, resulted in a higher rate of a positive biopsy yield compared to sampling of bone or disc (p = 0.006). Patients who received antibiotics had a higher rate of a positive biopsy yield (p = 0.014). In those with positive blood cultures, biopsy yielded the same antimicrobial susceptibility profile in 13/14 cases.

CONCLUSION

The presence of a paraspinal fluid collection or epidural abscess is correlated with positive biopsy yield, and paraspinal fluid collections should be targeted for biopsy. Other imaging findings did not correlate with biopsy yield. Biopsy may not offer additional information for patients with positive blood cultures.

The role of Propionibacterium acnes in and Modic type 1 changes : A literature review

Propionibacterium acnes (P. acnes) is part of the normal flora of human skin, oral cavity, intestinal tract and external ear canal. However, breach in the mucosa as well as ruptured annulus fibrosus provide favorable pathway for P. acnes to nucleus pulposus where it can proliferate under anaerobic condition. In past two decades many authors have identified P. acnes in routine culture of discs. There studies showed that almost 50% of discs cultured were positive for various organism, and in vast majority of culture positive disc, P. acnes was the primary organism isolated. However, there are few studies that refute the hypothesis that P. acnes has a role in pathogenesis of Modic type 1 changes. Identification of P. acnes in culture indicates the infective patho-mechanism in the pathogenesis of Modic type 1 changes, which may be ameable to antibiotic treatment. However, it is still difficult to identify which subset of these patients (patients with low back pain with type 1 Modic change) are infective in nature. Further investigation and more clinical trails will be required for clear identification of the infective subgroup among low back patient in general. J. Med. Invest. 67 : 21-26, February, 2020.

Chronic low back pain, bacterial infection and treatment with antibiotics

The contribution of bacterial infection to chronic low back pain and its treatment with antibiotics have generated considerable controversy in literature. If efficacious, antibiotics have the potential to transform the treatment of chronic low back pain in a significant subset of patients. Some microbiology studies of disc tissue from patients with CLBP have shown that bacteria are present, most likely due to infection, while others conclude they are absent or if found, it is due to surgical contamination. Clinical studies testing the efficacy of oral antibiotics to treat CLBP have either shown that the treatment is efficacious leading to significantly reduced pain and disability or that their effect is modest and not clinically significant. Critical review of the literature on CLBP, bacterial infection and treatment with antibiotics identified five well-designed and executed microbiology studies characterizing bacteria in disc samples that demonstrate that bacteria do infect herniated disc tissue, but that the bacterial burden is low and may be below the limits of detection in some studies. Two randomized, controlled clinical trials evaluating oral antibiotics in patients with CLBP indicate that for certain subsets of patients, the reduction in pain and disability achieved with antibiotic therapy may be significant. In patients for whom other therapies have failed, and who might otherwise progress to disc replacement or fusion surgery, antibiotic therapy may well be an attractive option to reduce the individual suffering associated with this debilitating condition. Additional clinical research is recommended to refine the selection of patients with CLBP caused or complicated by bacterial infection and most likely to respond to antibiotics, to optimize antibiotic therapy to maximize patient benefit, to minimize and manage side effects, and to address legitimate concerns about antibiotic stewardship.

Chronic low back pain, Modic changes and low-grade virulent infection: efficacy of antibiotic treatment

Chronic low back pain (CLBP) has consistently been associated with the longest number of years lived with a disability in global studies, while commonly used treatments for CLBP are largely ineffective. In 2013 a randomized, double-blind, controlled study demonstrated significant improvements in CLBP patients demonstrating Modic changes type 1 on their MRI scans and undergoing long-term oral antibiotic treatment (100 days). Much of the ensuing debate has focused on whether this was a true infection or contamination. Newer and more advanced technologies clearly point to an ongoing low-grade infection. We have reviewed all of the clinical trials published in the recent past and conclude that there is compelling evidence for the effect of long-term oral antibiotic treatment for this patient group.

Long-term oral antibiotic therapy has been shown to be effective for a subgroup of patients experiencing chronic low back pain and with Modic changes seen on their MRI scans. Newer and more sophisticated analyses have demonstrated that these Modic changes are often due to an ongoing low-grade infection. We provide an update of treatment results from the published literature and conclude that the evidence for the effectiveness of this new therapy is compelling and that further studies should focus on identifying which patients are best suited to undergo this form of treatment.

Major ceRNA regulation and key metabolic signature analysis of intervertebral disc degeneration

Background and objective

Intervertebral disc degeneration (IDD) is a complex multifactorial and irreversible pathological process. In IDD, multiple competing endogenous RNAs (ceRNA, including mRNA, lncRNA, and pseudogenes) can compete to bind with miRNAs. However, the potential metabolic signatures in nucleus pulposus (NP) cells remain poorly understood. This study investigated key metabolic genes and the ceRNA regulatory mechanisms in the pathogenesis of IDD based on microarray datasets.

Methods

We retrieved and downloaded four independent IDD microarray datasets from the Gene Expression Omnibus. Combining the predicted interactions from online databases (miRcode, miRDB, miRTarBase, and TargetScan), differentially expressed lncRNAs (DElncRNAs), miRNAs (DEmiRNAs), and mRNAs (DEmRNAs) were identified. A ceRNA network was constructed and annotated using GO and KEGG pathway enrichment analyses. Moreover, we searched the online metabolic gene set and used support vector machine (SVM) to find the critical metabolic DEmRNA(s) and other DERNAs. Differential gene expression was validated with a merged dataset.

Results

A total of 45 DEmRNAs, 36 DElncRNAs, and only one DEmiRNA (miR-338-3p) were identified in the IDD microarray datasets. GO and KEGG pathway enrichment analyses revealed that the DEmRNAs were predominantly enriched in the PI3K-Akt signaling pathway, MAPK signaling pathway, IL-17 signaling pathway, apoptosis, and cellular response to oxidative stress. Based on SVM screening, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK/FBPase) 2 is the critical metabolic gene with lower expression in IDD, and AC063977.6 is the key lncRNA with lower expression in IDD. The ceRNA hypothesis suggests that AC063977.6, miR-338-3p (high expression), and PFKFB2 are dysregulated as an axis in IDD.

Conclusions

The results suggest that lncRNA AC063977.6 correlate with PFKFB2, the vital metabolic signature gene, via targeting miR-338-3p during IDD pathogenesis. The current study may shed light on unraveling the pathogenesis of IDD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04109-8.

The Prevalence of Bacterial Infection in Patients Undergoing Elective ACDF for Degenerative Cervical Spine Conditions: A Prospective Cohort Study With Contaminant Control

STUDY DESIGN

Prospective cohort study.

OBJECTIVES

To determine the prevalence of bacterial infection, with the use of a contaminant control, in patients undergoing anterior cervical discectomy and fusion (ACDF).

METHODS

After institutional review board approval, patients undergoing elective ACDF were prospectively enrolled. Samples of the longus colli muscle and disc tissue were obtained. The tissue was then homogenized, gram stained, and cultured in both aerobic and anaerobic medium. Patients were classified into 4 groups depending on culture results. Demographic, preoperative, and postoperative factors were evaluated.

RESULTS

Ninety-six patients were enrolled, 41.7% were males with an average age of 54 ± 11 years and a body mass index of 29.7 ± 5.9 kg/m². Seventeen patients (17.7%) were considered true positives, having a negative control and positive disc culture. Otherwise, no significant differences in culture positivity was found between groups of patients. However, our results show that patients were more likely to have both control and disc negative than being a true positive (odds ratio = 6.2, 95% confidence interval = 2.5-14.6). Propionibacterium acnes was the most commonly identified bacteria. Two patients with disc positive cultures returned to the operating room secondary to pseudarthrosis; however, age, body mass index, prior spine surgery or injection, postoperative infection, and reoperations were not associated with culture results.

CONCLUSION

In our cohort, the prevalence of subclinical bacterial infection in patients undergoing ACDF was 17.7%. While our rates exclude patients with positive contaminant control, the possibility of contamination of disc cultures could not be entirely rejected. Overall, culture results did not have any influence on postoperative outcomes.

Correlation between the HIF-1α/Notch signaling pathway and Modic changes in nucleus pulposus cells isolated from patients with low back pain

BACKGROUND

The HIF-1α/Notch signaling pathway regulates cell proliferation, apoptosis, and metabolism in the intervertebral discs (IVDs) and is implicated in disc degeneration. The nucleus pulposus (NP) is an important structure adjacent to the IVDs. However, the role of the HIF-1α/Notch signaling pathway in NP cells obtained from patients with different Modic changes (MCs) remains unclear. The purpose of the present study was to investigate the role of HIF-1α and components of the Notch pathway in the NP obtained from patients with various MCs.

METHODS

A total of 85 NP tissue samples were collected from patients undergoing diskectomy for the treatment of low back pain. The NP tissues were divided into four groups based on the adjacent endplate degeneration, namely, MC I, II, III, and negative MC groups. The expression of HIF-1α and Notch-related components was measured and compared.

RESULTS

The expression of HIF-1α, Notch1, and Notch2 was gradually increased in the MC I and MC II groups compared with that in the negative MC group. HIF-1α and Notch-related components were rarely detected in the MC III group.

CONCLUSIONS

The expression of HIF-1α/Notch increased in the NP cells of patients with MC I and MC II. HIF-1α and Notch-related components are potential biomarkers and the HIF-1α/Notch signaling pathway may serve as a promising therapeutic target for disc degeneration in patients with MCs.

The Role of Cutibacterium acnes in Intervertebral Disc Inflammation

Recently, the role of infection of the intervertebral disc (IVD) with Cutibacterium acnes (C. acnes) as a contributor to disc-related low back pain (LBP) has been discussed. The aim of this study was to investigate whether and how C. acnes contributes to the inflammatory processes during IVD disease. The prevalence of C. acnes infection in human IVD tissue was determined by aerobic and anaerobic culture. Thereafter, primary human IVD cells were infected with a reference and a clinical C. acnes strain and analyzed for pro-inflammatory markers (gene/protein level). In a subsequent experiment, the involvement of the Toll-like receptor (TLR) pathway was investigated by co-treatment with sparstolonin B, a TLR2/4 inhibitor. We detected C. acnes in 10% of IVD biopsies (with either herniation or degeneration). Stimulating IVD cells with both C. acnes strains strongly and significantly upregulated expression of Interleukin (IL)-1β, IL-6, IL-8, and inducible nitric oxide synthase (iNOS). IL-6, cyclooxygenase (COX)-2, and iNOS expression was reduced upon TLR2/4 inhibition in 3 out of 5 donors, whereby responders and non-responders could not be differentiated by their basal TLR2 or TLR4 expression levels. We demonstrate that exposure of IVD cells to C. acnes induces an inflammatory response that may contribute to the development of discogenic LBP by involving TLR2/4 activation, yet only in a subgroup of patients. Whether the same response will be observed in vivo and where lower inoculums are present remains to be proven in future studies.

LncRNA MAGI2-AS3 is down-regulated in intervertebral disc degeneration and participates in the regulation of FasL expression in nucleus pulposus cells

Background

It is known that Fas ligand (FasL) is involved in the development of intervertebral disc degeneration (IDD). A recent study reported that lncRNA MAGI2-AS3 up-regulated the expression of FasL to promote breast cancer. Therefore, we investigated the roles that lncRNA MAGI2-AS3 might play in IDD.

Methods

A total of 66 IDD patients (IDD group) and 58 healthy volunteers (Control group) were recruited in this study. Quantitative real-time PCR (qRT-PCR) and western blot were used to investigate gene expression levels. Cell transfections were carried out to analyze gene interactions. The diagnostic value of lncRNA MAGI2-AS3 for IDD was assessed by ROC curve analysis.

Results

The expression levels of plasma lncRNA MAGI2-AS3 were lower in IDD patients compared to that in the control group. Down-regulation of lncRNA MAGI2-AS3 effectively distinguished IDD patients from the control group. The expression levels of plasma lncRNA MAGI2-AS3 were significantly increased after the treatments. Over-expression of lncRNA MAGI2-AS3 inhibited the expression of FasL, while the silencing of lncRNA MAGI2-AS3 promoted the expression of FasL in nucleus pulposus (NP) cells.

Conclusions

Therefore, lncRNA MAGI2-AS3 is down-regulated in IDD and participates in the regulation of FasL expression in nucleus pulposus (NP) cells.

Optimizing the safety of intradiscal platelet-rich plasma: an in vitro study with Cutibacterium acnes

Aim: The most common risk associated with intradiscal injection of platelet-rich plasma (PRP) is discitis with Cutibacterium acnes. It is hypothesized that antimicrobial activity of PRP can be enhanced through inclusion of leukocytes or antibiotics in the injectate. Materials & methods: Multiple PRP preparations of varying platelet and leukocyte counts were co-cultured with C. acnes with or without cefazolin, with viable bacterial colony counts being recovered at 0, 4, 24 and 48 hours post-inoculation. Results: A direct correlation between C. acnes recovery and granulocyte counts were observed. Conclusion: We observed the greatest antimicrobial activity with the leukocyte-rich, high platelet PRP preparation combined with an antibiotic in the injectate. However, cefazolin did not completely clear the bacteria in this assay.

Bacteria: back pain, leg pain and Modic sign-a surgical multicentre comparative study

PURPOSE

To compare bacterial findings in pain-generating degenerated discs in adults operated on for lumbar disc herniation (LDH), and mostly also suffering from low back pain (LBP), with findings in adolescent patients with non-degenerated non-pain-generating discs operated on for scoliosis, and to evaluate associations with Modic signs on magnetic resonance imaging (MRI). Cutibacterium acnes (Propionibacterium acnes) has been found in painful degenerated discs, why it has been suggested treating patients with LDH/LBP with antibiotics. As multidrug-resistant bacteria are a worldwide concern, new indications for using antibiotics should be based on solid scientific evidence.

METHODS

Between 2015 and 2017, 40 adults with LDH/LBP (median age 43, IQR 33-49) and 20 control patients with scoliosis (median age 17, IQR 15-20) underwent surgery at seven Swedish hospitals. Samples were cultured from skin, surgical wound, discs and vertebrae. Genetic relatedness of C. acnes isolates was investigated using single-nucleotide polymorphism analysis. DNA samples collected from discs/vertebrae were analysed using 16S rRNA-based PCR sequencing. MRI findings were assessed for Modic changes.

RESULTS

No bacterial growth was found in 6/40 (15%) LDH patients, compared with 3/20 (15%) scoliosis patients. Most positive samples in both groups were isolated from the skin and then from subcutis or deep within the wound. Of the four disc and vertebral samples from each of the 60 patients, 235/240 (98%) were DNA negative by bacterial PCR. A single species, C. acnes, was found exclusively in the disc/vertebra from one patient in each group. In the LDH group, 29/40 (72%) patients had at least one sample with growth of C. acnes, compared to 14/20 (70%) in the scoliosis group. Bacterial findings and Modic changes were not associated.

CONCLUSIONS

Cutibacterium acnes found in discs and vertebrae during surgery for disc herniation in adults with degenerated discs may be caused by contamination, as findings in this group were similar to findings in a control group of young patients with scoliosis and non-degenerated discs. Furthermore, such findings were almost always combined with bacterial findings on the skin and/or in the wound. There was no association between preoperative Modic changes and bacterial findings. Antibiotic treatment of lumbar disc herniation with sciatica and/or low back pain, without signs of clinical discitis/spondylitis, should be seriously questioned. These slides can be retrieved under Electronic Supplementary Material.

Is the discopathy associated with Modic changes an infectious process? Results from a prospective monocenter study

BACKGROUND

The local infectious origin and the putative role of Cutibacterium acnes (CA) of a particular subtype of discopathy (Modic 1) are still debated.

PURPOSE

To establish the association of CA in intervertebral disc (IVD) and Modic 1 discopathy in patients with low back pain.

METHODS

The prevalence of bacteria in IVD samples obtained by anterior approach in patient with chronic low back pain harboring Modic type 1, 2 or no Modic changes was compared to that measured in IVD samples obtained by posterior approach for sciatica. From 45 patients included in the study, 77 discs samples were obtained: 58 by anterior approach (32 Modic 1/2 changes, 26 without Modic change) and 19 by posterior approach. Conventional microbial cultures, universal 16S rRNA molecular detection and a CA specific PCR were performed.

RESULTS

12 /77 (15.6%) disc samples were culture positive. Among the 10 CA positive cultures, 5 out of 58 (8.6%) were identified from specimens obtained by anterior approach and 5/19 (26.3%) from posterior approach (p = 0.046). Moreover, the percentage of CA culture positive sample was statistically no different between the patient with or without Modic changes. The CA prevalence was lower through molecular, culture-free approaches: the universal 16S rRNA PCR was positive for 6 specimens, including one CA positive sample and the CA specific PCR was positive for one specimen obtained by posterior approach.

CONCLUSIONS

In spine surgery the prevalence of CA in culture was significantly higher in IVD samples collected through a posterior approach compared to an anterior approach, suggesting a contamination process. This study did not support the CA related local infectious origin of Modic 1 discopathy.

A review of microscopy-based evidence for the association of Propionibacterium acnes biofilms in degenerative disc disease and other diseased human tissue

PURPOSE

Recent research shows an increasing recognition that organisms not traditionally considered infectious in nature contribute to disease processes. Propionibacterium acnes (P. acnes) is a gram-positive, aerotolerant anaerobe prevalent in the sebaceous gland-rich areas of the human skin. A ubiquitous slow-growing organism with the capacity to form biofilm, P. acnes, recognized for its role in acne vulgaris and medical device-related infections, is now also linked to a number of other human diseases. While bacterial culture and molecular techniques are used to investigate the involvement of P. acnes in such diseases, definitive demonstration of P. acnes infection requires a technique (or techniques) sensitive to the presence of biofilms and insensitive to the presence of potential contamination. Fortunately, there are imaging techniques meeting these criteria, in particular, fluorescence in situ hybridization and immunofluorescence coupled with confocal laser scanning microscopy, as well as immunohistochemistry.

METHODS

Our literature review considers a range of microscopy-based studies that provides definitive evidence of P. acnes colonization within tissue from a number of human diseases (acne vulgaris, degenerative disc and prostate disease and atherosclerosis), some of which are currently not considered to have an infectious etiology.

RESULTS/CONCLUSION

We conclude that P. acnes is an opportunistic pathogen with a likely underestimated role in the development of various human diseases associated with significant morbidity and, in some cases, mortality. As such, these findings offer the potential for new studies aimed at understanding the pathological mechanisms driving the observed disease associations, as well as novel diagnostic strategies and treatment strategies, particularly for degenerative disc disease. These slides can be retrieved under Electronic Supplementary Material.

The bacteria-positive proportion in the disc tissue samples from surgery: a systematic review and meta-analysis

PURPOSE

The role of bacteria, especially Propionibacterium acnes (P. acnes), in human intervertebral disc diseases has raised attention in recent years. However, limited sample size of these studies and diverse bacteria-positive proportion made this topic still controversial. We aimed to review related articles and summarize the bacteria-positive proportion in these studies.

METHODS

We searched the PubMed, Cochrane Library, Embase for related literature from January 2001 to May 2018, and the reference articles were also searched. The random effects or fixed effects meta-analysis was used to pool the overall positive proportion or odds ratio of these studies.

RESULTS

We found 16 relevant articles and 2084 cases of the bacteria culture from surgery. Within the 16 included studies, 12 studies' results supported the infection in the discs. The pooled bacterial infection rate was 25.3%. The pooled P. acnes infection rate was 15.5%. The overall pooled P. acnes proportion in bacteria-positive discs was 56.4%. We also found that the presence of bacteria may contribute to the development of Modic change with the odds ratio as 1.27 (95% CI: 0.44-3.64), but this result is not significant due to heterogeneity, so further study is needed.

CONCLUSION

The existence of bacteria in the intervertebral discs was proved by many studies. However, the variety in sample collecting and culture methods is still obvious and the positive rate also fluctuated within the studies. Standardized and reliable methods should be taken to promote the study in the future. These slides can be retrieved under Electronic Supplementary Material.

The Relationship Between Low-Grade Infection and Degenerative Disk Disease: A Review of Basic Science and Clinical Data

Low back pain resulting from intervertebral disk degeneration is a cause of substantial disability and productivity loss. Over the past few years, growing evidence exists which suggests that low-grade bacterial infection, particularly infection with Cutibacterium acnes, may be associated with degenerative disk disease in the lumbar spine. Positive cultures are obtained in approximately 30% of intervertebral disk specimens removed at the time of surgery. In addition, one randomized trial has shown that antibiotic therapy for low back pain in patients with disk degeneration can slow the progression of degeneration and improve pain and disability levels. Although these results are encouraging, the link between infection and disk degeneration remains controversial. Investigators have attempted to address the limitations of clinical research by using translational methods and animal models. These methods have shown that seeding of the disk with bacteria can lead to increased local inflammation and an in vivo phenotype that is similar to human disk degeneration. This review seeks to provide an overview of the clinical, translational, and animal model data linking infection to disk degeneration. We review mechanisms for disk degeneration in the setting of infection and explore areas for future investigation.

Tandem Disc Herniation of the Lumbar and Cervical Spine: Case Series and Review of the Epidemiological, Pathophysiological and Genetic Literature

Introduction

Lumbar disc herniation (LDH) and cervical disc herniation (CDH) represent a relevant public health problem. Patients with symptomatic tandem herniations of the cervical and lumbar spine are rare and not described in the literature. In these patients, certain variables may predispose the development of disc herniation which could increase the understanding of the development of disc herniations. Our aim is to present the first case series of tandem disc herniation, and to elucidate whether tandem herniation is attributable to a certain propensity for disc herniation or not.

Methods 

From a prospective registry, patients with symptomatic tandem disc herniations were included, and the literature was reviewed on the comparative pathophysiology, genetics, and epidemiology of disc herniation and disc degeneration.

Results

Out of 3,156 patients with disc herniations in our registry, 16 presented with symptomatic tandem LDH and CDH that required discectomy. Therefore, we estimate the incidence of tandem disc herniation at 0.51% (95% confidence interval (CI): 0.26% - 0.75%) in the surgical population. The mean number of degenerated lumbar discs was 2.1 ± 1.1. Compared to the 1,241 patients with isolated LDH, no investigated factors were significantly associated with tandem herniations.

Conclusion

From a genetic, pathophysiological, and epidemiological position, disc herniation is not commonly a consequence of disc degeneration. Rather, degeneration and herniation seem to exist as two separate and distinctly different processes. Based on the literature, it is tenable that tandem disc herniation does not deviate from the normal pathophysiology, but rather occurs in the rare case that two individual herniated discs coincide.

Intervertebral disc penetration by antibiotics used prophylactically in spinal surgery: implications for the current standards and treatment of disc infections

PURPOSE

The presence of Propionibacterium acnes in a substantial component of resected disc specimens obtained from patients undergoing discectomy or microdiscectomy has led to the suggestion that this prominent human skin and oral commensal may exacerbate the pathology of degenerative disc disease. This hypothesis, therefore, raises the exciting possibility that antibiotics could play an important role in treating this debilitating condition. To date, however, little information about antibiotic penetration into the intervertebral disc is available.

METHODS

Intervertebral disc tissue obtained from 54 microdiscectomy patients given prophylactic cefazolin (n = 25), clindamycin (n = 17) or vancomycin (n = 12) was assayed by high-performance liquid chromatography, with cefaclor as an internal standard, to determine the concentration of antibiotic penetrating into the disc tissue.

RESULTS

Intervertebral disc tissues from patients receiving the positively charged antibiotic clindamycin contained a significantly greater percentage of the antibacterial dose than the tissue from patients receiving negatively charged cefazolin (P < 0.0001) and vancomycin, which has a slight positive charge (P < 0.0001).

CONCLUSION

Positively charged antibiotics appear more appropriate for future studies investigating potential options for the treatment of low-virulence disc infections. These slides can be retrieved under Electronic Supplementary Material.

Current concepts for lumbar disc herniation

PURPOSE

To present the pathophysiology, biology, clinical presentation, diagnosis, and current treatment options for lumbar disc herniation.

METHODS

A thorough literature search was undertaken in PubMed and Google Scholar to summarize the current knowledge and future perspectives on lumbar disc herniation.

RESULTS

Several changes in the biology of the intervertebral disc are thought to contribute to disc herniation; nevertheless, the exact inciting event leading to disc herniation is yet to be discovered. Non-operative treatments have stood the test of time as the first-line treatment for most patients with lumbar disc herniation; however, operative treatment remains the current gold standard, with minimally invasive endoscopic microdiscectomy techniques showing best results with respect to postoperative pain and function.

CONCLUSIONS

The exact event leading to disc herniation remains unclear. Non-operative treatments should be the first-line treatment for most patients with lumbar disc herniation. Operative treatment remains the current gold standard, with minimally invasive endoscopic microdiscectomy techniques showing best results with respect to postoperative pain and function. Regenerative medicine is promising.

Importance of Propionibacterium acnes hemolytic activity in human intervertebral discs: A microbiological study

Most patients with chronic lower back pain (CLBP) exhibit degenerative disc disease. Disc specimens obtained during initial therapeutic discectomies are often infected/colonized with Propionibacterium acnes, a Gram-positive commensal of the human skin. Although pain associated with infection is typically ascribed to the body's inflammatory response, the Gram-positive bacterium Staphylococcus aureus was recently observed to directly activate nociceptors by secreting pore-forming α-hemolysins that disrupt neuronal cell membranes. The hemolytic activity of P. acnes in cultured disc specimens obtained during routine therapeutic discectomies was assessed through incubation on sheep-blood agar. The β-hemolysis pattern displayed by P. acnes on sheep-blood agar was variable and phylogroup-dependent. Their molecular phylogroups were correlated with their hemolytic patterns. Our findings raise the possibility that pore-forming proteins contribute to the pathogenesis and/or symptomology of chronic P. acnes disc infections and CLBP, at least in a subset of cases.

Propionibacterium acnes induces discogenic low back pain via stimulating nucleus pulposus cells to secrete pro-algesic factor of IL-8/CINC-1 through TLR2-NF-κB p65 pathway

Latent infection of Propionibacterium acnes was considered as a new pathogeny for low back pain (LBP); however, there is no credible animal evidence or mechanism hypothesis. This study proved that P. acnes is a causative pathogen of bacteria-induced LBP and investigated its underlying mechanism. For this, P. acnes was firstly identified in patients' degenerated intervertebral disc (IVDs) samples. The results of patients' Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ), Japanese Orthopaedic Association (JOA), and Oswestry Disability Index (ODI) scores indicated that P. acnes-positive patients showed more severe LBP and physical disability. Then, a P. acnes-inoculated lumbar IVDs model was established in rats. The results of paw/foot withdrawal threshold and qRT-PCR indicated that P. acnes-inoculated rats had obvious LBP in behavioral evaluation and over-expression of substance P (SP) and calcitonin gene-related peptide (CGRP) in IVDs. Subsequently, enzyme-linked immunosorbent assay (ELISA) results demonstrated that increased expression of IL-8 or CINC-1 (the homolog of IL-8 in rats) in the P. acnes-positive IVDs of human and rats. The CINC-1 injected animal model proved that the cytokines were able to induce LBP. Finally, the co-culture experiments showed that nucleus pulposus cells (NPCs) were able to respond to P. acnes and secreted IL-8/CINC-1 via TLR-2/NF-κB p65 pathway. In conclusion, P. acnes had strong association with LBP by stimulating NPCs to secrete pro-algesic factor of IL-8/CINC-1 via TLR2/NF-κBp65 pathway. The finding may provide a promising alternative therapy strategy for LBP in clinical. KEY MESSAGES: Patients with P. acnes-positive IVDs tended to have more severe LBP, physical disability, and increased IL-8 expressions. P. acnes can induce LBP via IL-8/CINC-1 in IVDs. P. acnes stimulate the NPCs to secrete pro-algesic factor of IL-8/CINC-1 via TLR2/NF-κBp65 pathway.

Degenerate-disc Infection Study with Contaminant Control: Discussion on the Research Methods

OBJECTIVE

The role of bacterial infection in the causation of disc degeneration and its consequences is controversial. The current evidence is limited to underpowered studies, with the majority of such studies having only an internal contaminant arm, and only one study having a control arm with a non-degenerate disc population. The Degenerate-disc Infection Study with Contaminant Control (DISC) study includes a control arm and an internal contaminant control to resolve these shortcomings.

METHODS

The study is designed as a case-control study: cases are patients undergoing surgery for degenerated disc pathology and controls are patients undergoing surgery for non-degenerate pathology, such as trauma, scoliosis or tumor cases.

RESULTS

This study is part of a multi-centric trial involving six spine centers with 15 spine surgeons contributing. The DISC study methodology, rationale and controversies are presented here. The predominant issue is how to interpret contamination. We present our algorithm for the DISC study to address this. For disc samples that are positive concurrently with positive paraspinal tissue sample, the result will be interpreted as contamination. For positive disc samples with a negative paraspinal tissue culture result, the interpretation of this result will be infection. If cultures for both disc sample and paraspinal tissue sample are negative, then the result is interpreted as non-infected. If the disc culture is negative but paraspinal tissue culture is positive, then it is treated as a contaminant.

CONCLUSIONS

Future large-scale studies are required with a good control arm, a contamination arm, and histopathological correlations.

Is IL-1β Further Evidence for the Role of Propionibacterium acnes in Degenerative Disc Disease? Lessons From the Study of the Inflammatory Skin Condition Acne Vulgaris

The pathogenesis of degenerative disc disease is a complex and multifactorial process in which genetics, mechanical trauma, altered loading and nutrition present significant etiological factors. Infection of the intervertebral disc with the anaerobic bacterium Propionibacterium acnes is now also emerging as a potentially new etiological factor. This human commensal bacterium is well known for its long association with the inflammatory skin condition acne vulgaris. A key component of inflammatory responses to P. acnes in acne appears to be interleukin (IL)-1β. Similarly, in degenerative disc disease (DDD) there is compelling evidence for the fundamental roles of IL-1β in its pathology. We therefore propose that P. acnes involvement in DDD is biologically very plausible, and that IL-1β is the key inflammatory mechanism driving the host response to P. acnes infection. Since there is a solid theoretical basis for this phenomenon, we further propose that the relationship between P. acnes infection and DDD is causal.

Quantification of Propionic Acid in the Bovine Spinal Disk After Infection of the Tissue With Propionibacteria acnes Bacteria

STUDY DESIGN

Research.

OBJECTIVE

The goal of this study was to investigate whether Propionibacteria acnes infection of the intervertebral disc can be detected noninvasively by nuclear magnetic resonance (NMR) spectroscopy.

SUMMARY OF BACKGROUND DATA

Microbiological studies of surgical samples suggest that a significant subpopulation of back pain patients may have occult disc infection with P. acnes bacteria. This hypothesis is further supported by a double-blind clinical trial showing that back pain patients with Modic type 1 changes may respond to antibiotic treatment. Because significant side effects are associated with antibiotic treatment, there is a need for a noninvasive method to detect whether specific discs in back pain patients are infected with P acnes bacteria.

METHODS

P. acnes bacteria were obtained from human patients. NMR detection of a propionic acid (PA) in the bacteria extracts was conducted on 500 MHz high-resolution spectrometer, whereas in vivo NMR spectroscopy of an isolated bovine disk tissue infected with P. acnes was conducted on 7 T magnetic resonance imaging scanner.

RESULTS

NMR spectra of P. acnes metabolites revealed a distinct NMR signal with identical chemical shits (1.05 and 2.18 ppm) as PA (a primary P. acne metabolite). The 1.05 ppm signal does not overlap with other bacteria metabolites, and its intensity increases linearly with P. acnes concentration. Bovine disks injected with P. acnes bacteria revealed a very distinct NMR signal at 1.05 ppm, which linearly increased with P. acnes concentration.

CONCLUSION

The 1.05 ppm NMR signal from PA can be used as a marker of P. acnes infection of discs. This signal does not overlap with other disc metabolites and linearly depends on P. acnes concentration. Consequently, NMR spectroscopy may provide a noninvasive method to detect disc infection in the clinical setting.

LEVEL OF EVIDENCE

N/A.

Inflammatory response of disc cells against Propionibacterium acnes depends on the presence of lumbar Modic changes

PURPOSE

Intervertebral disc with Propionibacterium acnes (P. acnes) is suggested to be an etiology of Modic type I changes in the adjacent bone marrow. However it is unknown if disc cells can respond to P. acnes and if bone marrow cells respond to bacterial and disc metabolites draining from infected discs.

METHODS

Human disc cells (n = 10) were co-cultured with 10- and 100-fold excess of P. acnes over disc cells for 3 h and 24 h. Lipopolysaccharide was used as positive control. Expression of IL1, IL6, IL8, and CCL2 by disc cells was quantified by quantitative PCR. Lipase activity was measured in culture supernatants (n = 6). Human vertebral bone marrow mononuclear cells (BMNCs) (n = 2) were cultured in conditioned media from disc cell/P. acnes co-cultures and expression of IL1, IL6, IL8, and CCL2 was measured after 24 h.

RESULTS

All disc cells responded to lipopolysaccharide but only 6/10 responded to P. acnes with increased cytokine expression. Cytokine increase was time- but not P. acnes concentration-dependent. Disc cell responsiveness was associated with the presence of lumbar Modic changes in the donor. Lipase activity was increased independent of disc cell responsiveness. BMNCs responded with inflammatory activity only when cultured in supernatants from responsive disc cell lines.

CONCLUSION

Disc cell responsiveness to P. acnes associates with the presence of lumbar Modic changes. Furthermore, bone marrow cells had an inflammatory response to the cocktail of disc cytokines and P. acnes metabolites. These data indicate that low virulent P. acnes infection of the disc is a potential exacerbating factor to Modic changes.

Low virulence bacterial infections in cervical intervertebral discs: a prospective case series

STUDY DESIGN

A prospective cross-sectional case series study.

OBJECTIVE

To investigate the prevalence of low virulence disc infection and its associations with characteristics of patients or discs in the cervical spine.

BACKGROUND

Low virulence bacterial infections could be a possible cause of intervertebral disc degeneration and/or back pain. Controversies are continuing over whether these bacteria, predominantly Propionibacterium acnes (P. acnes), represent infection or contamination. However, the current studies mainly focus on the lumbar spine, with very limited data on the cervical spine.

METHODS

Thirty-two patients (20 men and 12 women) who underwent anterior cervical fusion for degenerative cervical spondylosis or traumatic cervical cord injury were enrolled. Radiological assessments included X-ray, CT, and MRI of the cervical spine. Endplate Modic changes, intervertebral range of motion, and disc herniation type were evaluated. Disc and muscle tissues were collected under strict sterile conditions. Samples were enriched in tryptone soy broth and subcultured under anaerobic conditions, followed by identification of the resulting colonies by the PCR method.

RESULTS

Sixty-six intervertebral discs were excised from thirty-two patients. Positive disc cultures were noted in eight patients (25%) and in nine discs (13.6%). The muscle biopsy (control) cultures were negative in 28 patients and positive in 4 patients (12.5%); three of whom had a negative disc culture. Seven discs (10.6%) were positive for coagulase-negative Staphylococci (CNS) and two discs were positive for P. acnes (3.0%). A younger patient age and the extrusion or sequestration type of disc herniation, which represented a complete annulus fibrous failure, were associated with positive disc culture.

CONCLUSIONS

Our data show that CNS is more prevalent than P. acnes in degenerative cervical discs. The infection route in cervical discs may be predominantly through an annulus fissure. Correlation between these infections and clinical symptoms is uncertain; therefore, their clinical significance needs to be investigated in the future. These slides can be retrieved under Electronic Supplementary Material.

Propionibacterium acnes induces intervertebral disc degeneration by promoting nucleus pulposus cell apoptosis via the TLR2/JNK/mitochondrial-mediated pathway

Evidence suggests that intervertebral disc degeneration (IVDD) can be induced by Propionibacterium acnes (P. acnes), although the underlying mechanisms are unclear. In this study, we analyzed the pathological changes in degenerated human intervertebral discs (IVDs) infected with P. acnes. Compared with P. acnes-negative samples, P. acnes-positive IVDs showed increased apoptosis of nucleus pulposus cells (NPCs) concomitant with severe IVDD. Then, a P. acnes-inoculated IVD animal model was established, and severe IVDD was induced by P. acnes infection by promoting NPC apoptosis. The results suggested that P.acnes-induced apoptosis of NPCs via the Toll-like receptor 2 (TLR2)/c-Jun N-terminal kinase (JNK) pathway and mitochondrial-mediated cell death. In addition, P. acnes was found to activate autophagy, which likely plays a role in apoptosis of NPCs. Overall, these findings further validated the involvement of P. acnes in the pathology of IVDD and provided evidence that P. acnes-induced apoptosis of NPCs via the TLR2/JNK pathway is likely responsible for the pathology of IVDD.

Lumbar Disc Herniation

PURPOSE OF REVIEW

Substantial advancements have been made in the cause, diagnosis, imaging, and treatment options available for patients with lumbar disc herniation (LDH). We examined the current evidence and highlight the concepts on the frontline of discovery in LDH.

RECENT FINDINGS

There are a myriad of novel etiologies of LDH detailed in recent literature including inflammatory factors and infectious microbes. In the clinical setting, recent data focuses on improvements in computer tomography as a diagnostic tool and non-traditional injection options including tumor necrosis alpha inhibitors and platelet-rich plasma. Operative treatment outcomes have focused on minimally invasive endoscopic approaches and demonstrated robust 5-year post-operative outcomes. Advances in the molecular etiology of LDH will continue to drive novel treatment options. The role of endoscopic treatment for LDH will continue to evolve. Further research into10-year outcomes will be necessary as this surgical approach continues to gain widespread popularity.