Modic changes in the adjacent vertebrae due to disc material infection with Propionibacterium acnes in patients with lumbar disc herniation

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.

Association of modic changes and postoperative surgical site infection after posterior lumbar spinal fusion

PURPOSE

Postoperative surgical site infection is one of the most serious complications following spine surgery. Previous studies have reported Modic changes (MC) represent a subclinical infection. This study aims to investigate the relation between Modic changes and surgical site infection after posterior lumbar fusion surgery.

METHODS

We retrospectively reviewed the records of 424 patients who received posterior lumbar fusion. Preoperative clinical and radiological parameters were recorded. Primary outcome was the rate of postoperative surgical site infection. Covariates included age, body mass index (BMI), sex, hypertension, diabetes mellitus, chronic heart failure, Pfirrmann classification, fused levels, and operation duration. The presence of Modic changes was used as an exposition variable, and adjusted for other risk factors in multivariate analyses.

RESULTS

Of the 424 patients, 30 (7%) developed an acute surgical site infection. Infection had no relation to age, sex, BMI, and comorbidities. There were 212 (50%) patients with MC, and 23 (10.8%) had a surgical site infection, compared to 212 (50%) patients without MC in which there were 7 (3.3%) surgical site infections. MC was associated with surgical site infection in univariate analysis (odds ratio [OR] = 3.56, 95% confidence interval [CI]: 1.49-8.50, p = 0.004) and multivariate logistic regression analysis (OR = 3.05, 95% CI: 1.26-7.37, p = 0.013). There was statistically significant between specific type (p = 0.035) and grade of MCs (p = 0.0187) and SSI.

CONCLUSIONS

MCs may be a potential risk factor for SSI following posterior lumbar spinal intervertebral fusion. Type I and grade C MCs showed a higher infection rate compared with other MC types and grades.

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.

The area ratio of Modic changes has predictive value for postoperative surgical site infection in lumbar spine surgery: a retrospective study

BACKGROUND

Increasing evidence suggests an association between Modic changes (MC) and subclinical infection and inflammatory reactions. However, the relationship between preoperative MC and surgical site infection (SSI) has not been fully explored. This study aims to investigate the correlation between MC and SSI.

METHODS

A retrospective analysis was conducted on patients (n = 646) who underwent single-level lumbar spine surgery for lower back pain in our hospital between 2018 and 2023. According to the Centers for Disease Control and Prevention (CDC) criteria, the patients were divided into an SSI group (n = 40) and a Non-SSI group (n = 606). Univariate analysis was performed to determine the statistical differences in variables between the two groups, and the variables with significant differences were included in a multivariable logistic regression analysis to identify independent risk factors for SSI. Receiver operating characteristic (ROC) curve analysis was performed on the independent risk factors.

RESULTS

The SSI group and the Non-SSI group exhibited significant differences in diabetes prevalence, MC prevalence, Total endplate score (TEPS) and area ratio of MC (P < 0.05). Age, gender, American Society of Anesthesiologists(ASA)score, hypertension, coronary heart disease (CHD), chronic obstructive pulmonary disease (COPD), MC classification, and the location of MC in the endplate showed no significant differences (P > 0.05). Multivariate binary logistic regression analysis was performed on the variables with significant differences, and the results indicated a significant correlation between TEPS (P = 0.009) and the area ratio of MC changes (P = 0.001) with SSI. ROC curve analysis was performed on the TEPS and area ratio of MC changes, and the results showed that the diagnostic value of TEPS (AUC: 0.641; CI: 0.522-0.759) is lower than the area ratio of MC (AUC: 0.722; CI: 0.621-0.824), and the combined diagnosis did not significantly improve the diagnostic value (AUC: 0.747; CI: 0.653-0.842). The area ratio of MC had moderate diagnostic value for SSI (AUC: 0.722; CI: 0.621-0.824), with a cut-off value of 24.62% determined by the Youden index (sensitivity: 69.2%; specificity: 73.1%), and for every 1% increase in the area ratio of MC changes, the risk of SSI in MC patients increased by 10.3% (OR = 1.103; CI: 1.044-1.167).

CONCLUSION

The area ratio MC and the TEPS are independent risk factors for SSI after lumbar spine surgery. The predictive value of the area ratio of MC is greater than TEPS, and when the two are combined, the predictive value is not significantly improved. When the rate of MC exceeds 24.62%, caution should be exercised regarding the occurrence of SSI.

Modic change is associated with increased BMI but not autoimmune diseases in TwinsUK

PURPOSE

Low back pain (LBP) is one of the largest causes of morbidity worldwide. The aetiology of LBP is complex, and many factors contribute to the onset. Bone marrow lesions within the vertebra adjacent to an intervertebral degenerate disc named Modic change (MC) have been suggested as a diagnostic subgroup of LBP. Autoimmune response has been proposed to be one of the causes that promote the development of MC. The aim of the current investigation is to assess prevalence and severity of MC and LBP in participants with an autoimmune disease diagnosis in a well-documented cohort of adult twin volunteers.

METHODS

Multivariate generalized mixed linear models (GLMM) were implemented in order to calculate the association between having an autoimmune disorder and MC prevalence, width and severe and disabling LBP. The model was corrected for family structure as well as for covariates such as age, BMI and smoking.

RESULTS

No association was found between diagnosis of autoimmune disorder and MC. Interestingly, BMI was independently associated with MC width but not to MC prevalence. These results help to shed light on the relationship between MC and autoimmunity as well as the role of BMI in the development of the lesions.

CONCLUSION

This study is the first to examine autoimmune disorders and MC prevalence in a large, population-based female cohort. The study was well powered to detect a small effect. No association was found between having a diagnosis of one or more autoimmune conditions and MC prevalence, width or LBP.

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.

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.

Non-surgical therapy for the treatment of chronic low back pain in patients with Modic changes: A systematic review of the literature

Background

In absence of uniform therapeutic recommendations, knowledge of the available treatment options for Modic changes (MCs) patients and their safety and effectiveness would be crucial and significant for clinicians and such patients.

Objectives

The aim of this study was to provide a systematic review of available studies on non-surgical treatments of MCs.

Methods

We performed a systematic review of multiple electronic databases including PubMed, Web of Science, Embase, Cochrane Library, and China National Knowledge Infrastructure for the period until 31st August 2021 to search for studies on non-surgical treatments for MCs in accordance with the guidance of the Cochrane Handbook. Potential studies were screened by their titles and abstracts. The methodological quality of the included studies was independently evaluated by two authors. Final recommendations for the included interventions were developed based on grades of recommendations. The narrative format was adopted to synthesize the findings of the present work.

Results

Fifth studies involving a total of 1147 patients were identified for this systematic review. The results of this review demonstrated that spinal manipulation has been suggested as an alternative option for patients with MCs. However, there was insufficient evidence to support that patients with MCs can benefit from the medication and wearing the rigid lumbar brace. Moreover, the rationale and safety for the use of antibiotics in such patients remain highly controversial. Low evidence revealed that exercise therapy might decrease pain intensity only for special subgroups of MCs patients.

Conclusions

There is not yet enough evidence to suggest that non-surgical treatments are useful for patients with MCs. Further high-quality, multicenter trials are required to validate the effectiveness of these non-surgical treatments.

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.

The Effect of Cutibacterium acnes Infection on Nerve Penetration in the Annulus Fibrosus of Lumbar Intervertebral Discs via Suppressing Oxidative Stress

Modic changes (MCs) and low back pain are highly correlated and an economic burden to the society. Previous studies have shown that Cutibacterium acnes (C. acnes) infection can lead to MCs. The purpose of this study was to clarify whether and how C. acnes contributes to oxidative stress and nerve growth that potentially leads to low back pain. Neurons from the hippocampus or dorsal root ganglion (DRG) of Sprague-Dawley (SD) rats were cocultured with annulus fibrosus cells (AFCs) with or without the presence of the C. acnes supernatant in vitro. Cell viability, neurite length, oxidative stress, and neuro-related gene expression were examined. Furthermore, samples from the patients with MCs and SD rat model of MCs were used to validate the nerve growth results. Neurons from both the hippocampus and DRG showed neurites when cocultured with AFCs in the environment with/without the C. acnes supernatant. The average neurite length was significantly longer when exposed to the C. acnes supernatant in the hippocampal neuron (217.1 ± 90.0 μm versus 150.1 ± 68.1 μm in the control group) and in the DRG neuron (229.1 ± 91.3 μm versus 149.2 ± 64.8 μm in the control group). Hippocampal neurons showed upregulated expression levels of NeuN, Map2, and Psd95, while upregulation was only seen in Tuj-1 in DRG neurons. Suppressed oxidative stress could be observed using axon growth symbols. Degenerated disc structures and abnormal bone remodelling were found in animal models and clinical samples of MCs, with astrocytes, microglia, and neurons in the disc. Therefore, C. acnes infection was found to cause back pain in the presence of MCs by promoting nerve penetration into the annulus fibrosus by suppressing oxidative stress.

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.

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.

Sheep as a Potential Model of Intradiscal Infection by the Bacterium Cutibacterium acnes

The anaerobic bacterium Cutibacterium acnes has been increasingly linked to the development of degenerative disc disease (DDD), although causality is yet to be conclusively proven. To better study how this organism could contribute to the aetiology of DDD, improved animal models that are more reflective of human disc anatomy, biology and mechanical properties are required. Against this background, our proof-of concept study aimed to be the first demonstration that C. acnes could be safely administered percutaneously into sheep intervertebral discs (IVDs) for in vivo study. Following our protocol, two sheep were successfully injected with a strain of C. acnes (8.3 × 10⁶ CFU/disc) previously recovered from a human degenerative disc. No adverse reactions were noted, and at one-month post inoculation all triplicate infected discs in our first animal grew C. acnes, albeit at a reduced load (5.12 × 10⁴ to 6.67 × 10⁴ CFU/disc). At six months, no growth was detected in discs from our second animal indicating bacterial clearance. This pilot study has demonstrated the feasibility of safe percutaneous injection of C. acnes into sheep IVDs under fluoroscopic guidance. The design of follow-up sheep studies to investigate the potential of C. acnes to drive pathological changes within infected discs should now be pursued.

Pro-Inflammatory and Neurotrophic Factor Responses of Cells Derived from Degenerative Human Intervertebral Discs to the Opportunistic Pathogen Cutibacterium acnes

Previously, we proposed the hypothesis that similarities in the inflammatory response observed in acne vulgaris and degenerative disc disease (DDD), especially the central role of interleukin (IL)-1β, may be further evidence of the role of the anaerobic bacterium Cutibacterium (previously Propionibacterium) acnes in the underlying aetiology of disc degeneration. To investigate this, we examined the upregulation of IL-1β, and other known IL-1β-induced inflammatory markers and neurotrophic factors, from nucleus-pulposus-derived disc cells infected in vitro with C. acnes for up to 48 h. Upon infection, significant upregulation of IL-1β, alongside IL-6, IL-8, chemokine (C-C motif) ligand 3 (CCL3), chemokine (C-C motif) ligand 4 (CCL4), nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), was observed with cells isolated from the degenerative discs of eight patients versus non-infected controls. Expression levels did, however, depend on gene target, multiplicity and period of infection and, notably, donor response. Pre-treatment of cells with clindamycin prior to infection significantly reduced the production of pro-inflammatory mediators. This study confirms that C. acnes can stimulate the expression of IL-1β and other host molecules previously associated with pathological changes in disc tissue, including neo-innervation. While still controversial, the role of C. acnes in DDD remains biologically credible, and its ability to cause disease likely reflects a combination of factors, particularly individualised response to infection.

Molecular detection of Propionibacterium acnes in biopsy samples of intervertebral disc with modic changes in patients undergoing herniated disc surgery

Background and Objectives:

Recent studies have hypothesized that sterile disc infection with the anaerobic Propionibacterium acnes, recently renamed Cutibacterium acnes, occurs in people with intervertebral disc (IVD) herniation. This study aimed to examine the presence of P. acnes in patients who have Low back pain (LBP) with Modic changes observed in their Magnetic Resonance Imaging (MRI).

Materials and Methods:

Thirty-seven patients who were candidates for surgery due to disc herniation and demonstrated Modic changes in MRI were included in the study. Before the surgery, the level of pain in patients was assessed using the visual analog score (VAS). All patients were asked to fill in the Oswestry Low Back Pain Disability Questionnaire. Intervertebral disc changes observed in MRI were recorded for all patients. Then, during surgery, sterile intervertebral disc samples were taken. P. acnes detection was performed using PCR in the laboratory. Data analysis with Chi-squared test, independent samples t-test, and Mann-Whitney U test in SPSS 18.0.

Results:

The mean age of 37 patients equaled 43.64 years and the mean duration of symptoms was 11.05 months. In molecular examination, of the 37 individuals, the genome of P. acnes was positive in 23 cases (62.2%) and negative in 14 (37.8%). The relationship between VAS, disability score, changes in MRI, and patients’ age with the positivity of the intervertebral disc sample was also assessed. Of these variables, only age was significantly correlated with the positive molecular finding, such that with an increase in age, the probability of positive findings was increased (p = 0.022).

Conclusion:

Based on the results, lumbar disc infection with P. acnes may play a significant role in causing Modic changes and the progression of the disease in patients with LBP.

Correlation Between Modic Changes and Bacterial Infection: A Causative Study

STUDY DESIGN

Prospective nonrandomized study.

OBJECTIVE

Objective of the study was to ascertain etiological correlation between Modic changes (MC) and bacterial infection through 16s DNA sequencing in patients with chronic low backache.

SUMMARY OF BACKGROUND DATA

Modic changes are common on magnetic resonance imaging (MRI) of patients with low back pain and are strongly associated with low back pain. Various factors are associated with the etiology; of these, degeneration and mechanical factors are most common. Some studies have also found etiological relation between MC and infection.

MATERIAL AND METHOD

The study involved 20 patients of either sex (age range, 20-65 years) who were investigated for blood count, erythrocyte sedimentation rate, and quantitative C-reactive protein. The intervertebral disc removed during discectomy from each patient was sent for polymerase chain reaction (PCR) study. We have targeted the conserved gene of the bacteria (ie, 16s ribosomal DNA) and used a universal eubacteria nested-amplification protocol that may detect picograms of bacterial DNA.

RESULT

Among the 20 cases of patients who had low back pain and MC in MRI, 13.5% showed raised leucocytosis, 28.6% showed raised erythrocyte sedimentation rate, 72.7% showed raised quantitative C-reactive protein, and 90% of the disc sample showed presence of bacteria in PCR study.

CONCLUSION

MC may have an infective etiology.

LEVEL OF EVIDENCE

4.

Presence of preoperative Modic changes and severity of endplate damage score are independent risk factors for developing postoperative surgical site infection: a retrospective case-control study of 1124 patients

PURPOSE

There is increasing evidence of an association between Modic changes (MC) and subclinical infection. However, the association of MC with postoperative surgical site infection (SSI) has not been adequately probed. This study primarily aimed to investigate a probable association between preoperative MC, total endplate damage score (TEPS), and SSI.

METHODS

A retrospective analysis of 1124 patients who underwent surgery in a single institution (2016-2018) was performed, using both univariate and multiple logistic regression analyses to identify independent risk factors for SSI.

RESULTS

The prevalence of SSI was 4% (44/1124 patients), with no association with age or sex. The prevalence of MC in the SSI group was significantly higher-79.54% (35/44) compared to 58.79% (635/1080) (p value = 0.006) in the control group with no specific relation to type or location of MC. A higher TEPS was associated with SSI (p value = 0.009). A receiver operating characteristic (ROC) curve for TEPS values to assess predictiveness of SSI showed TEPS ≥ 5.5 to have a better sensitivity of 84% than 72% for a TEPS ≥ 6.5. Univariate analysis showed TEPS > 6 (odds ratio 3.887) to have a stronger association with SSI than the presence of MC (odds ratio 2.725). Among various types of surgeries, discectomy had a higher association with SSI (p value = 0.03) when compared to fusion (p value = 0.071). However, multiple logistic regression analysis revealed only TEPS > 6, presence of MC and hypothyroidism as independent risk factors for SSI.

CONCLUSION

Our data suggest that preoperative MC and TEPS > 6 are independent risk factors for developing surgical site infections. MC could be foci of chronic subclinical infection and not mere markers of degeneration, as initially described.

Osteal Tissue Macrophages Are Involved in Endplate Osteosclerosis through the OSM-STAT3/YAP1 Signaling Axis in Modic Changes

Modic changes (MCs) are radiographic manifestations of lumbar degenerative diseases. Various types of MCs are often associated with endplate osteosclerosis. Osteal tissue macrophages (Osteomacs) were reported to be crucial for bone homeostasis and bone repair, but whether osteomacs participate in the endplate osteosclerosis in MCs remained unclear. In this study, we tried to explore the critical role of osteomacs in regulating osteogenesis in MCs. We collected MCs from patient samples and developed a Propionibacterium acnes-induced rat MCs model, using microcomputed tomography and immunohistochemistry to detect the endplate bone mass and distribution of osteomacs. In patients' MCs, osteomacs increased in endplate subchondral bone, especially in Modic type II. Endplate in Modic type III presented a stable osteosclerosis. In rat MCs model, osteomacs increased in the bone hyperplasia area but not in the inflammation area of the endplate region, whereas the distribution of osteomacs was consistent with the area of osteosclerosis. To further explore the functions of osteomacs in vitro, we isolated osteomacs using MACS technology and found osteomacs secreted oncostatin M (OSM) and strongly promoted osteoblast differentiation rather than osteoclast through the mechanism of OSM-mediated tyrosine phosphorylation and interaction of STAT3 and Yes-associated protein 1 (YAP1). STAT3 phosphorylation inhibition or YAP1 knockdown attenuated OSM-mediated osteoblast differentiation. Finally, we confirmed that blockade of OSM in vivo using anti-OSM-neutralizing Ab prevented endplate osteosclerosis in rat MCs model. Taken together, these findings confirmed that endplate osteosclerosis in MCs was accompanied by an increased number of osteomacs, which regulated osteogenesis via the OSM-STAT3/YAP1 signaling axis.

Vertebral Bone Marrow and Endplate Assessment on MR Imaging for the Differentiation of Modic Type 1 Endplate Changes and Infectious Spondylodiscitis

On magnetic resonance (MR) imaging, Modic type 1 (MT1) endplate changes and infectious spondylodiscitis share similar findings. Therefore, this study investigated vertebral bone marrow and endplate changes to enable their differentiation. The lumbar spine MR examinations of 91 adult patients were retrospectively included: 39 with MT1; 19 with early spondylodiscitis without abscess; and 33 with advanced spondylodiscitis with abscess. The assessment included percentage of bone marrow edema on sagittal short tau inversion recovery images, and the signal ratio of edema to unaffected bone and endplate contour (normal; irregular, yet intact; blurred; destructive) on sagittal unenhanced T1-weighted images. Differences were tested for statistical significance by Chi-square test and mixed model analysis of variance. The MR diagnostic accuracy in differentiating MT1 and spondylodiscitis was assessed by cross-tabulation and receiver-operating characteristic analysis. The endplate contours, edema extents, and T1-signal ratios of MT1 (extent, 31.96%; ratio, 0.83) were significantly different (p < 0.001) from early spondylodiscitis (56.42%; 0.60), and advanced spondylodiscitis (91.84%; 0.61). The highest diagnostic accuracy (sensitivity, 94.87%; specificity, 94.23%; accuracy, 94.51%) in identifying MT1 was provided by an irregular, yet intact endplate contour. This may be a useful MR feature for the differentiation between MT1 and spondylodiscitis, particularly in its early stage.

Hyperbaric oxygen treatment: A complementary treatment modality of Modic changes?

Modic changes (MCs) have attracted great interest in recent years. The complex process of MC development and progression seems to involve interplay between mechanical, infective, inflammatory, and degenerative processes that cannot be clearly differentiated. Based on signal intensity on T1- and T2-weighted MRI scans, MCs can be divided three types: Type 1, Type 2, and Type 3. Predominantly Type 1 MCs are commonly associated with chronic low back pain that is unresponsive to classic treatment options. Infection with low-virulent anaerobic microorganisms, most commonly Propionibacterium acnes, has been implicated in MC development following a disc herniation when a tear enables bacteria to enter the disc. Recent studies in patients with chronic low back pain following a lumbar disc herniation associated with Type 1 MCs have reported promising results following prolonged systemic antibiotic treatment with amoxicillin-clavulanate. Hyperbaric oxygen therapy, as primary or adjuvant treatment in association combination with systemic antibiotics or anti-inflammatory therapy, could offer important advantages in treating patients with suspected low-virulent disc infections due to anaerobic microorganisms associated with Type 1 MCs. We believe that hyperbaric oxygenation could contribute to faster resolution of Type 1 MCs and associated pain through multiple effects-including direct antimicrobial effects through formation of reactive oxygen species (ROS), altering the favorable low oxygen tension milieu such that it becomes unfavorable for bacterial growth and survival, and anti-biofilm effects. Additionally, hyperbaric oxygenation could contribute to faster pain resolution via direct and indirect anti-inflammatory effects. As an adjuvant treatment administered in combination with systemic antibiotics, HBOT could increase the sensitivity of Propionibacterium acnes to antimicrobial drugs under hyperoxic conditions, resulting in faster MC resolution. Overall, the faster infection resolution, diminished bacterial load, and anti-inflammatory effects due to reduced cytokine expression and levels of infectious by-products could lead to faster pain resolution following HBOT, and a significant improvement of quality of life in these patients.

Disc inflammation and Modic changes show an interaction effect on recovery after surgery for lumbar disc herniation

Purpose

To study the interaction between Modic changes (MC) and inflammation by macrophages in the disc, in relation to clinical symptoms before and after discectomy for lumbar disc herniation.

Methods

Disc tissue was embedded in paraffin and stained with haematoxylin and CD68. Subsequently, tissue samples were categorized for degree of inflammation. Type of MC was scored on MRI at baseline. Roland Disability Questionnaire (RDQ) score and visual analogue scale for back pain and leg pain separately were considered at baseline and 1-year follow-up post-surgery. Main and interaction effects of MC and inflammation were tested against clinical outcome questionnaires. In addition, this analysis was repeated in bulging and extruded discs separately.

Results

Disc material and MRI’s of 119 patients were retrieved and analysed. Forty-eight patients demonstrated mild inflammation, 45 showed moderate inflammation, and 26 showed considerable inflammation. In total, 49 out of 119 patients demonstrated MC. Grade of disc inflammation did not associate with the presence of MC. At baseline, no main or interaction effects of MC and inflammation were found on the clinical scores. However, during follow-up after discectomy, significant interaction effects were found for RDQ score: Only in patients with MC at baseline, patients remained significantly more disabled (3.2 points p = 0.006) if they showed considerable disc inflammation compared to patients with mild inflammation. The additional analysis showed similar results in extruded discs, but no significant effects in bulging discs.

Conclusions

An interaction effect of MC and disc inflammation by macrophages is present. Only in patients with MC, those with considerable inflammation recover less satisfactory during follow-up after surgery.

Graphic abstract

These slides can be retrieved under Electronic Supplementary Material.

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.

Cutibacterium acnes in Spine Pathology: Pathophysiology, Diagnosis, and Management

Cutibacterium acnes, long thought to be skin flora of pathological insignificance, has seen a surge in interest for its role in spine pathology. C acnes has been identified as a pathogen in native spine infection and osteomyelitis, which has implications in the management compared with more commonly recognized pathogens. In addition, It has also been recognized as a pathogen in postoperative and implant-associated infections. Some evidence exists pointing to C acnes as an unrecognized source of otherwise aseptic pseudarthrosis. Recently, it is hypothesized that low virulent organisms, in particular C acnes, may play a role in degenerative disk disease and the development of Modic end plate changes found in MRI. To this end, controversial implications exist in terms of the use of antibiotics to treat certain patients in the setting of degenerative disk disease. C acnes continues to remain an expanding area of interest in spine pathology, with important implications for the treating spine surgeon.

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.

Propionibacterium acnes Infection in Disc Material and Different Antibiotic Susceptibility in Patients With Lumbar Disc Herniation

Background

Low back pain is an important, worldwide clinical problem from which human populations are suffering. It has been suggested that Propionibacterium acnes is associated with low back pain. The objective of this clinical study is to evaluate the P. acnes infection in the disc material and antibiotic susceptibility in patients with disc herniation.

Methods

A total of 120 patients with disc herniation surgery were enrolled in the study. The samples were excited during discectomy and then cultured in both anaerobic and aerobic incubations. Minimum inhibitory concentration (MIC) was performed for determination of antibiotic susceptibility.

Results

Of 120 samples, 60 (50%) samples were positive for microorganisms. Disc herniation was at the level of L4-L5 in 63 cases and L5-S1 in 57 cases.

Conclusions

According to the results and presence of P. acnes in more than 35% of the cultured samples, the presence of P. acnes in lumbar disc herniation is a suspected element leading to this condition. After analysis of the antibiotics, the lowest MIC value was identified for amoxicillin, ciprofloxacin, erythromycin, rifampicin, tetracycline, vancomycin; the moderate MIC value was for fusidic acid; and the highest MIC value was for gentamicin and trimethoprim.

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.

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.

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.

The distribution of infection with Propionibacterium acnes is equal in patients with cervical and lumbar disc herniation

BACKGROUND

Cervical and back pains are important clinical problems affecting human populations globally. It is suggested that Propionibacterium acnes (P. acnes) is associated with disc herniation. The aim of this study is to evaluate the distribution of P. acnes infection in the cervical and lumbar disc material obtained from patients with disc herniation.

METHODS AND MATERIAL

A total of 145 patients with mean age of 45.21 ± 11.24 years who underwent micro-discectomy in cervical and lumbar regions were enrolled into the study. The samples were excited during the operation and then cultured in the anaerobic incubations. The cultured P. acnes were detected by 16S rRNA-based polymerase chain reaction.

RESULTS

In this study, 145 patients including 25 cases with cervical and 120 cases with lumbar disc herniation were enrolled to the study. There was no significant difference in the age of male and female patients (p = 0.123). P. acnes infection was detected in nine patients (36%) with cervical disc herniation and 46 patients (38.3%) with lumbar disc herniation and no significant differences were reported in P. acnes presence according to the disc regions (p = 0.508.). Moreover, there was a significant difference in the presence of P. acnes infection according to the level of lumbar disc herniation (p = 0.028).

CONCLUSION

According to the results, the presence of P. acnes is equal in patients with cervical and lumbar disc herniation. There was a significant difference in the distribution of P. acnes infection according to level of lumbar disc herniation.

LEVEL OF EVIDENCE

II.

Propionibacterium acnes biofilm is present in intervertebral discs of patients undergoing microdiscectomy

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.

P. acnes-Driven Disease Pathology: Current Knowledge and Future Directions

This review discusses the biology and behavior of Propionibacterium acnes (P. acnes), a dominant bacterium species of the skin biogeography thought to be associated with transmission, recurrence and severity of disease. More specifically, we discuss the ability of P. acnes to invade and persist in epithelial cells and circulating macrophages to subsequently induce bouts of sarcoidosis, low-grade inflammation and metastatic cell growth in the prostate gland. Finally, we discuss the possibility of P. acnes infiltrating the brain parenchyma to indirectly contribute to pathogenic processes in neurodegenerative disorders such as those observed in Parkinson's disease (PD).

Can the pattern of vertebral marrow oedema differentiate intervertebral disc infection from degenerative changes?

AIM

To evaluate whether various patterns of bone marrow oedema could be used to discriminate between infection and degenerative change.

MATERIALS AND METHODS

Seventy patients with imaging features suspicious for discitis and available clinical follow-up were blindly reviewed for vertebral marrow oedema on sagittal short-tau inversion recovery (STIR) images according to the following patterns: I, vertebra oedema is adjacent to the intervertebral space and sharply-marginated; II, vertebral oedema is adjacent to the intervertebral space but not sharply marginated from normal marrow or involves the entire vertebral body; and III, vertebral oedema is distant from the endplate with intervening hypointense marrow signal.

RESULTS

Of 45 patients with a clinical diagnosis of discitis, pattern II was the most common oedema pattern (64%). Approximately 20% and 9% of discitis patients showed patterns I and III, respectively. In patients with degenerative changes, 44% patients showed pattern I, 32% showed pattern II, and 24% showed pattern III. Pattern II had a sensitivity, specificity, and positive predictive value of 0.64, 0.68, and 0.78 for diagnosing spine infection, respectively.

CONCLUSIONS

Although bone marrow oedema in infective discitis most often extends from the disc space and has indistinct margins, the oedema may also have sharp margins or be remote from the involved intervertebral space. Bone marrow oedema patterns of infective discitis overlap with those of degenerative disease and are not sufficiently reliable to exclude infection in cases with magnetic resonance imaging findings suggestive of discitis.