Table 1.
Summary of studies included
| Studies finding bacteria in disc material = 28 | Participants | Bacteria identified | Lab techniques | Control group/control samples | Other measures | Results |
|---|---|---|---|---|---|---|
| (Agarwal, Golish et al. 2011) |
52 single-level lumbar microdiscectomy patients No antibiotic use exclusion criteria noted |
C. acnes Peptostreptococcus spp. S. aureus CoNS spp. |
Routine bacterial culture Incubated for 5d under standard anaerobic conditions | No control or comparison group created & no control specimens taken | No host markers of infection assessed. Duration of LBP symptoms and prior surgeries (n = 11) recorded | 10/52 (19%) patients had positive cultures: C. acnes (predominantly) |
| (Aghazadeh, Salehpour et al. 2017) |
120 lumbar disc herniation patients (87 MC) Antibiotic use 1mth prior to surgery excluded |
C. acnes CoNS Gram-negative bacilli Micrococcus Corynebacterium Neisseria spp. |
Anaerobic & aerobic culture incubation glovebox each for 7d. Sub-culture and Gram-staining to identify C. acnes Specific C. acnes 16S rRNA PCR primers |
No control or comparison group created. Paravertebral muscle (control) samples taken | No host markers of infection assessed. No pain scores assessed | 60 patients including 42 MC had positive cultures. Predominantly C. acnes was found |
| (Albert, Lambert et al. 2013) |
61 single-level lumbar disc herniation surgery patients Antibiotic use 14d prior to surgery excluded |
C. acnes CoNS Gram-positive cocci Gram-negative rod Neisseria species |
5 tissue samples collected from each patient. Columbia blood agar plates, aerobic & anaerobic incubation for 7d. Presumptive C. acnes 16S PCR rRNA priming & amplification |
No control or comparison group created & no control specimens taken; longitudinal study with repeat measures | No host markers of infection assessed. FU MRIs conducted | 28 patients with positive cultures, 80% of anaerobic bacterial positive culture patients developed new MC within ~ 1.5 years. Bacterial proliferation in disc increased risk of developing new MC |
| (Arndt, Charles et al. 2012) |
83 lumbar disc replacement (degeneration) patients (32 MC1 & 25 MC2) No antibiotic use exclusion criteria noted |
C. acnes CoNS S. aureus Enterobacter cloacae Enterobacter aerogenes Escherichia coli Micrococcus Corynebacterium minutissimum Corynebacterium coyleae Microbacterium Brevibacterium Rothia dentocariosum Enterococcus faecalis Streptococcus intermedius |
Disc samples divided into three parts for analysis, 3 anaerobic media plate cultures 5d with supplementation. Peptone glucose yeast broth for 10d. Plates & broth screened daily for growth | No control or comparison group created & no control specimens | Additional histological examination showed host inflammatory cells in 33% of positive culture & 5% of negative culture specimens | 40/83 had positive cultures. Males and MC2 higher rates of microbiological findings. Bacteria in almost half disc & predominantly in males. No correlation with MC1, positive cultures twice as prevalent in MC2 participants |
| (Bivona, Camacho et al. 2021) |
96 anterior cervical discectomy fusion patients 165 discs Long-term antibiotic use excluded |
C. acnes CoNS Staphylococcus spp. Stretococcus spp. Kocuria rhizophila |
Aerobic & anaerobic 5d culturing. If growth; identified subcultures & Gram-staining, followed by MALDI-TOF MS | No control or comparison group created. Logus colli muscle (control) specimens taken | FU assessment of surgical success. No host markers of infection assessed. No pain scores assessed | Discs with positive control were excluded. 24/83 (29%) bacterial positive. Only study to report Kocuria rhizophila in disc material |
| (Capoor, Ruzicka et al. 2016) |
290 lumbar disc herniation patients 290 (caudal to avoid statistical bias) discs Antibiotic use 1mth prior to surgery excluded |
C. acnes CoNS Alpha-haemolytic streptococci |
Two disc samples, one for culturing undertaken 2 h after acquisition (specimens not frozen). Anaerobic culturing 14d. Frozen sample PCR | ‘Infective’ (≥ 1000 CFU/ml) C. acnes group compared with < 1000 CFU/ml or C. acnes negative. No control specimens | Pre-operative clinical data captured (straight leg tests, sensory & motor assessments). No host markers of infection assessed. No pain scores assessed | C. acnes identified in 115 (40%) of samples, at an ‘infective’ level in 39 (11%) |
| (Capoor, Ruzicka et al. 2017) |
368 lumbar disc herniation patients 368 discs Antibiotic use 1mth prior to surgery excluded |
C. acnes Staphylococcus saccharolyticus Staphylococcus epidermidus Staphylococci heamolyticus |
Extended anaerobic culture. MALDI-TOF. C. acnes genotyping. C. acnes specific 16S probe for FISH & DNA dye for CLSM | ‘Infective’ (≥ 1000 CFU/ml) C. acnes group compared with < 1000 CFU/ml or C. acnes negative. No control specimens | FISH/CLSM visualisation of host inflammatory cells & bacterial load assessed. No pain scores assessed | 162/368 positive for bacterial growth; 119 were C. acnes. No predominance of any C. acnes phylotype. C. acnes seen ‘in situ’ within biofilm |
| (Chen, Wang et al. 2018) |
32 cervical fusion patients (21 MC, 28 degenerative disc & 4 trauma patients) 66 discs Antibiotic use 1mth prior to surgery excluded |
CoNS C. acnes Staphylococcus epidermidis Staphylococci haemolyticus Staphylococci capitis |
Tryptone soy broth and 14 day sealed anaerobic bag incubation. Negative control samples (no tissue) also cultured. Gram-staining and PCR | Degenerate disc and trauma control groups. Sternocleidomastoid muscle specimens | FU assessment of surgical success. No host markers of infection assessed. No pain scores assessed. Disc herniations classified 1–4 severity, based on MRI | 9 discs from 8 patients were 16S positive. Infection in degenerate cervical discs associated with younger age, and complete annulus tear but not MC |
| (Coscia, Denys et al. 2016) |
87 patients 169 discs (30 cervical herniation, 30 lumbar herniation, 30 lumbar discogenic pain, 30 scoliosis control discs & 45 trauma/ deformity control discs) No antibiotic use exclusion criteria noted |
C. acnes CoNS |
Traditional anaerobic culture & Gram-staining | 5 comparison groups of discs created, importantly 2 non-degenerative control groups. No comparison specimens | WBC assessed & histological examination undertaken. No identification of microorganisms, host inflammation or infection with histology. MRI assessment of 27 patients (41 discs). # MC not published | Positive cultures found in 45% of discs, sub-clinical infection occurred at a much higher rate in herniation than control patients. No bacterial correlation with MC. Researchers did not separate bacteria from biofilm, perhaps explaining histology findings. Microbes cultured at higher rates in degenerate discs than control specimens |
| (Drago, Romano et al. 2020) |
39 LBP surgery patients (16 MC2 & 23 MC-free) No antibiotic use exclusion criteria noted |
C. acnes Bacillus spp. Lactobacillus spp. Staphylococcus hominis |
Nucleus pulpous samples. Cultured & incubated 48 h/15d. Vitek 2 microbial identification | MC2 compared with MC-free patients. No comparison specimens | Full blood count, ESR, CRP & serum electrophoresis | 6 (37.5%) MC2 samples and 1 (4.3%) MC-free sample cultured positive |
| (Fritzell, Bergström et al. 2004) |
10 lumbar disc herniation patients w. large protrusions/extrusions No antibiotic use exclusion criteria noted |
Bacillus cereus Citrobacter braaki Citrobacter freundii |
16S rRNA PCR | No control or comparison group created & no control specimens | No host markers of infection assessed. Pain assessed pre-operatively & 6 weeks post | Small pilot study. 3 specimens from 2 patients were 16S positive |
| (Georgy, Vaida et al. 2018) |
48 cervical surgery patients (13 MC1) No antibiotic use exclusion criteria noted |
C. acnes | Aerobic and anaerobic culture plates (4 different agars) incubated for 7d | MC1 compared with other degenerative disc cases. No control specimens taken | No host markers of infection assessed. No pain scores assessed |
54% MC1 and 20% MC1-free samples C. acnes positive C. acnes in degenerative disc material. MC1 discs affected at a higher rate |
| (Javanshir, Salehpour et al. 2017) |
145 patients (25 cervical & 120 lumbar herniation) Antibiotic use 1mth prior to surgery excluded |
C. acnes | Aerobic & anaerobic blood agar glove box, 7d incubation. Sub-culturing to CBA plates, 24 h incubation. Gram-staining all colonies with presumptive C. acnes rapid ID kit. Specific C. acnes 16S PCR primers | Compared C. acnes proliferation between cervical and lumbar herniation. No control specimens taken | No host markers of infection assessed. No pain scores assessed | 55 (38%) C. acnes positive. No difference in bacterial positivity between cervical and lumbar disc samples. Sub-clinical disc infection not isolated to lumbar spine |
| (Najafi, Mahmoudi et al. 2020) |
37 lumbar herniation with MC patients Antibiotic use 60d prior to surgery excluded |
C. acnes | Culturing and PCR C. acnes specific primers | No control or comparison group created & no control specimens | VAS & disability scores taken prior to surgery. No host markers of infection assessed | 23 (62%) bacteria positive, with no difference between disc protrusion, extrusion or budging. No association between VAS or disability scores and bacterial findings |
| (Ohrt-Nissen, Fritz et al. 2018) |
65 (51 lumbar herniation (H) & 14 control (trauma surgery) patients (C)) Excluded if antibiotic used for 14d within 6mth of surgery |
(H) C. acnes (H&C) Staphylococcus epidermidis (H&C) Staphylococcus capitis (H) Micrococcus luteus (H) Gemmiger formicilis (H) Kocuria dechangensis (C) Faecalibacterium prausnitzii (C) Staphylococcus aureus (C) Bacillus simplex |
16S rRNA PCR and BLAST Bacterial aggregates and host inflammatory cells examined with FISH/CLSM |
Control participants group. No control specimens taken | FISH/CLSM analysis, visualised host inflammatory cells. No pain assessments taken | 16S rRNA detected in 16/51 cases & 7/14 controls. Bacterial aggregates & host inflammatory cells observed in bacterial positive cases only & not in control samples |
| (Rajasekaran, Tangavel et al. 2017) |
22 patients (15 herniation, 5 degenerative & 2 non-degenerative). All disc from lumbar spine No antibiotic use exclusion criteria noted |
73 bacterial proteins identified including 53 C. acnes & 17 S. epidermidis specific proteins | Dual 16S rRNA universal primer & proteomic analysis of host defence proteins | Non-degenerative control participants. Herniated and degenerated discs compared. No control specimens taken | Proteomics evaluation assessed host defence proteins. No pain assessments taken |
Host defence signature responses to disc herniation and degeneration specific bacterial proteins identified in degenerate disc material. Host defence proteins suggestive of infection |
| (Rajasekaran, Soundararajan et al. 2020) |
24 participants (8 MRI healthy, 8 disc degeneration & 8 disc herniation) No antibiotic use exclusion criteria noted |
424 different microbial species. Highly abundant phyla: Proteobacteria, Parcubacteria, Firmicutes, Cyanobacteria & Actinobacteria |
Genomic DNA extraction and universal amplification (V1-V9 16S rRNA primers) Proteins: Mass spectrometry analysis. Proteomics analysis |
3 groups compared: healthy, degenerated and herniated discs. No control specimens taken | Proteomics evaluation assessed host defence proteins. No pain assessments taken | Microbiome signatures for healthy, degenerated and herniated discs |
| (Rollason, McDowell et al. 2013) |
64 lumbar disc herniation patients Antibiotic use 14d prior to surgery excluded |
C. acnes Predominance of phylotype strains II & III in disc material Presumptive C. acnes & Staphylococcus spp. identified S. aureus |
Nucleus extracted from disc sample, disc dissected into five other parts. Aerobic & anaerobic incubation 7d Nucleotide sequencing of recA housekeeping gene to differentiate C. acnes phylotypes multiple disc samples analysed including separate nucleus analysis | No control or comparison group created & no control specimens | No host markers of infection assessed. No pain scores assessed |
24 (38%) C. acnes growth 28% isolates type I A 9% isolates type I B 52% isolates type II 11% isolates type III C. acnes phylotypes in disc differ from those on the skin |
| (Salehpour, Aghazadeh et al. 2019) |
120 single-level lumbar disc herniation patients Antibiotic use 1mth prior to surgery excluded |
C. acnes | Blood agar plates, 7d aerobic & anaerobic glovebox. Sub-cultured & 24 h anaerobic incubation. Presumptive C. acnes rapid ID followed by 16S rRNA PCR | No control or comparison group created & no control specimens |
No host markers of infection assessed. No pain scores assessed Study went on to examined C. acnes resistance to several different antibiotics |
60 (50%) samples were positive for microorganisms study designed to assess C. acnes response to variety of antibiotic drugs |
| (Singh, Siddhlingeswara et al. 2020) |
20 LBP MC patients No antibiotic use exclusion criteria noted |
Identified 16S rRNA gene positive disc specimens | 16S rRNA Universal eubacteria nested amplification protocol | No control or comparison group created & no control specimens | Measured or leucocytes, ESR and CRP taken. No pain scores assessed | 18 (90%) samples demonstrated 16S rRNA gene presence |
| (Stirling, Worthington et al. 2001) |
140 sciatica & LBP patients 36 discectomy (severe sciatica) No antibiotic use exclusion criteria noted |
C. acnes CoNS Corynebacterium propinquum |
Incubated & sub-cultured in broth for 2, 7 & 21d. Gram-staining for microorganisms. Measured C. acnes CFU in positive samples | Compared serology inflammatory markers in moderate and extreme sciatica patients. No control specimens taken | Serum IgG titres relative to lipid S antigen & CRP levels assessed. Undertook clinical assessment, no pain measures reported | 19/36 (53%) positive cultures, 16/19 (84%) C. acnes identified in disc samples. First study to link sub-clinical infection with disc pathology. Higher rate of inflammatory serology associated with more severe sciatica and need for surgery |
| (Tang, Wang et al. 2018) |
80 LBP discectomy patients (25 MC) Antibiotic use 1mth prior to surgery excluded |
C. acnes CoNS |
5 disc segments: 3 culture media plates & 2 enriched broth. Results read at 7 & 14d. If bacterial growth; universal primers & 16S rRNA PCR used for identification | MC compared with MC-free samples. Surrounding muscle & ligament samples taken | Measured severity of disc degeneration. VAS pain measure | 23 samples positive (3 others excluded, suspicious for contamination). Higher rates of positive cultures in MC samples. No relationship between degeneration severity, nor VAS & bacterial infection |
| (Tang, Chen et al. 2019) |
179 single-level lumbar disc herniation patients Antibiotic use 1mth prior to surgery excluded |
C. acnes CoNS |
3 culture media plates, 2 broth—aerobic & anaerobic culturing for 7 & 14d. Bacterial growth 16S rRNA PCR | Participants compared by age & grouped according to severity of disc degeneration. Surrounding muscle & ligament samples taken | Intervertebral disc height measured (degeneration severity). No pain measures reported | 33 samples had positive bacterial growth (6 others excluded, suspicious for contamination). Higher infection rates in younger participants & in those with more degenerated discs |
| (Withanage, Pathirage et al. 2019) |
101 lumbar disc herniation patients Antibiotic use 14d prior to surgery excluded |
CoNS sup C.acnes Gemella morbilorum Staphylococci spp. |
Enrichment broth & 3 aerobic media cultures followed by additional enrichment and incubation. 3 anaerobic media cultures for 2, 7 & 21d | Skin scapings & muscle biopsy control samples taken. No control or comparison group created | No host markers of infection assessed. No pain scores assessed | 18 disc samples positive, 12 for aerobes (CoNS), 6 for anaerobes. First study to identify Gemella morbilorum in disc material. No control samples microbe positive |
| (Yuan, Zhou et al. 2017) |
76 LBP and/or sciatica discectomy patients (70 herniation) 76 discs Antibiotic use 1mth prior to surgery excluded |
C. acnes 3 unidentified species |
Soy broth culture with serum anaerobic glovebox for 14d C. acnes specific primer & 16S rRNA PCR |
Surrounding muscle tissue samples taken. No control or comparison group created | WBC counts taken, MRI signs of discitis assessed, other infection signs (fever/chills) assessed. No pain measures reported | 23/76 samples showed anaerobic growth, 20 C. acnes, 4 of these samples were considered contaminated |
| (Yuan, Chen et al. 2018) |
Sub-set from Yuan, Zhou et al. 2017 15 C. acnes positive & 15 C. acnes negative discs |
NA | DNA extracted with boiling and bands visualised with UV photography | C. acnes positive samples matched with negative samples for cytokine analysis. Samples from Yuan 2017 | Histological disc examination & cytokine quantified in disc tissue. Measures of TFN-a, IL-1b, IL-6, IL-8, MCP-1, MIP-1a, IP-10 & neutrophils | Visible bacteria present in 7 C. acnes positive and no C. acnes negative specimens. Little correlation between inflammatory markers and C. acnes positivity; only IL-8, MIP-1a & neutrophils significant |
| (Zhou, Chen et al. 2015) |
46 LBP/sciatica patients (MC1 5, MC2 13) Antibiotic use 1mth prior to surgery excluded |
C. acnes |
Soy broth culture with serum incubated in anaerobic glovebox for 14d followed by 16S rRNA PCR with C. acnes specific primers |
Samples with annular tear compared to those without. Surrounding muscle control specimens taken | Disc height measured. No host markers of infection assessed. No pain scores assessed | 11 (23.9%) discs tested positive for 16S rRNA. Only discs with annular tears tested positive. No relationships between MC or sciatica & C. acnes in the disc found |
| Evidence that spinal disc material is sterile n = 9 | Participants | Bacteria identified | Lab techniques | Control group/control samples | Other measures | Results |
|---|---|---|---|---|---|---|
| (Ahmed-Yahia, Decousser et al. 2019) |
45 lumbar spine surgery patients (24 MC1, 8MC2) 77 discs Excluded if antibiotic used for 15d within 3 m of surgery |
C. acnes Staphylococcus epidermidis C. avidum Staphylococcus spp. Streptococcus spp. |
Chocolate culture media for 5 and 10 days followed by broth if clouded. Bacterial identification with MALDI-TOF MS. Universal 16S rRNA PCR (+ 18S) | Compared anterior (58) and posterior (19) approaches for spine surgery | Pain duration & VAS recorded. No host markers of infection assessed | 12/77 (15.6%) specimens were culture positive. Disc bacterial positivity attributed to posterior surgical approach. No difference in MC 0, 1 or 2 culture rates |
| (Alamin, Munoz et al. 2017) |
44 lumbar herniation patients (7 MC1, 4 MC2) No antibiotic use exclusion criteria noted |
None | qPCR | No control or comparison group created & no control specimens | No host markers of infection assessed. No pain scores assessed | No evidence of bacterial gene in excised disc samples |
| (Alexanyan, Aganesov et al. 2020) |
64 degenerative lumbar spine disease patients (64 MC) 80 discs |
C. acnes | Aerobic & anaerobic culture. VITEK 2 microbial identification. Staining & electronic microscopy | No control or comparison group created & no control specimens | Histological assessment of samples. No pain scores assessed | 1/64 (1.6%) patient had disc tissue with bacteria identified. No histological confirmation of bacteria or host inflammation |
| (Ben-Galim, Rand et al. 2006) |
30 LBP or sciatica lumbar excision patients 120 discs Antibiotic use 14d prior to surgery excluded |
CoNS | Multiple culture mediums, anaerobic incubation 14d | No control or comparison group created & no control specimens | No host markers of infection assessed. No pain scores assessed | 4 disc specimens from 2 participants grew CoNS cultures |
| (Carricajo, Nuti et al. 2007) |
54 lumbar disc herniation patients Antibiotic use history recorded – not excluded |
C. acnes Anaerobic streptococci Actinomyces sup CoNS |
4 culture media 10d/20d | Surrounding tissue & environment control taken. No control or comparison group created | CRP & WBC levels evaluated. No pain scores assessed | Positive cultures in 2 (3.7%) disc samples and 10 (18.5%) muscle controls. Surgery air samples also positive for C. acnes |
| (Fritzell, Welinder-Olsson et al. 2019) | 60 participants (40 LBP/ herniation & 20 scoliosis control) (MC 23/40, 18/20) |
C. acnes Streptococcus spp. Lactococus lactis Corynebacterium Burkholderiales |
Culturing & universal 16S rRNA PCR | Non-degenerative disc controls included. Skin & surrounding tissue samples taken | No host markers of infection assessed. No pain scores assessed | 2 participants with disc only positive samples. 85% participants had one or more samples positive for bacteria. High rates in muscle & skin control samples. No difference between herniation and scoliosis groups in positive disc samples. No association between MC and positive bacterial growth |
| (Li, Dong et al. 2016) |
22 lumbar disc herniation patients (2 MC1, 6 MC2) 30 discs Antibiotic use 1mth prior to surgery excluded |
CoNS Staphylococcus epidermidis |
Only used nucleus pulpous. Aerobic & anaerobic culturing 10d incubation. Identified with Gram-staining, morphology, oxygen tolerance & Api20A | Paravertebral muscle control samples taken. Comparison groups of degeneration according to Pfirrmann classification | No host markers of infection assessed. No pain scores assessed | 3/30 specimens positive for bacteria. No association with MC |
| (Rao, Maharaj et al. 2020) |
812 participants (550 disc & paraspinal samples, 191 disc only, 46 sham; paraspinal only & 25 control; trauma patients) No antibiotic use exclusion criteria noted |
Acinetobacter Candida Corybacterium Cutibacterium (C. acnes) Staphylococcus |
Aerobic & anaerobic culture: 4 different plates for 7 & 14 days | Non-degenerate controls used. Surrounding fat, ligament and muscle tissue control samples taken | Sub-section of patients’ samples underwent histological examination for inflammation evidence. No pain scores assessed | Positive cultures in discs: 33/191 (17%) ‘disc only’, 146/554 (27%) ‘disc + control’, 12/25 (48%) control group samples. High rates of positive bacteria in paravertebral control samples. Largest study investigating bacteria in disc pathology, findings suggest contamination |
| (Rigal, Thelen et al. 2016) |
313 participants (303 MC1, 58 MC2) 385 discs No antibiotic use exclusion criteria noted |
C. acnes S. epidermidis Citrobacter freundii Saccharopolyspora hirsuta |
Anaerobic culture 15d. Plates/growth then underwent histological examination | No control specimens taken | Life & health satisfaction scales, pain rating scales at BL, 3,6 & 12 mths. Histological examination of disc tissue for host inflammatory response & neutrophils | 6/385 (1.5%) samples positive cultures. The origin of inflammation in disc degeneration is unknown. No association between bacteria positive disc and outcome |