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Published on: July 8, 2021
Ribosomal PCR assay of excised intervertebral discs from patients undergoing single-level primary lumbar
Todd F Alamin1, Marcus Munoz2, Alicia Zagel2
1Department of Orthopaedic Surgery, Stanford University School of Medicine, 450 Broadway St, Pavillion A FL 1 MC6110, Redwood City, CA, 94063, USA. tfalamin@stanford.edu.
Purpose:
To determine the presence of infectious microorganisms in the herniated discs of immunocompetent patients, using methodology that we hoped would be of higher sensitivity and specificity than has been reported in the past. Recent studies have demonstrated a significant rate of positive cultures for low virulent organisms in excised HNP samples (range 19-53%). These studies have served as the theoretical basis for a pilot trial, and then, a well done prospective randomized trial that demonstrated that systemic treatment with antibiotics may yield lasting improvements in a subset of patients with axial back pain. Whether the reported positive cultures in discectomy specimens represent true positives is as yet not proven, and critically important if underlying the basis of therapeutic approaches for chronic low back pain.
Methods:
This consecutive case series from a single academic center included 44 patients with radiculopathy and MRI findings of lumbar HNP. Patients elected for lumbar microdiscectomy after failure of conservative management. All patients received primary surgery at a single spinal level in the absence of immune compromise. Excised disc material was analyzed with a real-time PCR assay targeting the 16S ribosomal RNA gene followed by amplicon sequencing. No concurrent cultures were performed. Inclusion criteria were as follows: sensory or motor symptoms in a single lumbar nerve distribution; positive physical examination findings including positive straight leg raise test, distributional weakness, and/or a diminished deep tendon reflexes; and magnetic resonance imaging of the lumbar spine positive for HNP in a distribution correlating with the radicular complaint.
Results:
The PCR assay for the 16S rRNA sequence was negative in all 44 patients (100%). 95% CI 0-8%.
Conclusions:
Based on the data presented here, there does not appear to be a significant underlying rate of bacterial disc infection in immunocompetent patients presenting with radiculopathy from disc herniation.
Insights
This study found no evidence of bacterial infection in herniated discs of immunocompetent patients. Advanced PCR testing on 44 patients confirmed negative results, questioning previous culture-based findings of low-virulent organisms.
Area of Science:
- Orthopedics
- Microbiology
- Neurosurgery
Background:
- Previous studies suggested a significant rate of low-virulent organisms in herniated disc samples.
- These findings formed the basis for trials investigating antibiotic treatment for chronic low back pain.
- The validity of positive cultures in discectomy specimens remains unproven and critical for understanding treatment efficacy.
Purpose of the Study:
- To determine the presence of infectious microorganisms in herniated discs of immunocompetent patients.
- To employ highly sensitive and specific methodologies for microorganism detection.
- To clarify the role of bacterial infection in chronic low back pain.
Main Methods:
- A consecutive case series of 44 immunocompetent patients undergoing lumbar microdiscectomy for radiculopathy.
- Analysis of excised disc material using real-time PCR targeting the 16S ribosomal RNA gene, followed by amplicon sequencing.
- Exclusion of patients with immune compromise and concurrent cultures.
Main Results:
- The PCR assay for the 16S rRNA sequence was negative in all 44 patients (100%).
- The 95% confidence interval for positive results was 0-8%.
- No evidence of bacterial infection was detected in the analyzed disc samples.
Conclusions:
- The study found no significant underlying rate of bacterial disc infection in immunocompetent patients with radiculopathy due to disc herniation.
- These results challenge previous findings based on culture methods.
- Further investigation may be needed to understand the etiology of chronic low back pain in these patients.
