BACKGROUND: The relationship between intervertebral disc degeneration and chronic infection by Propionibacterium acnes is controversial with contradictory evidence available in the literature. Previous studies investigating these relationships were under-powered and fraught with methodical differences; moreover, they have not taken into consideration P. acnes' ability to form biofilms or attempted to quantitate the bioburden with regard to determining bacterial counts/genome equivalents as criteria to differentiate true infection from contamination. The aim of this prospective cross-sectional study was to determine the prevalence of P. acnes in patients undergoing lumbar disc microdiscectomy. METHODS AND FINDINGS: The sample consisted of 290 adult patients undergoing lumbar microdiscectomy for symptomatic lumbar disc herniation. An intraoperative biopsy and pre-operative clinical data were taken in all cases. One biopsy fragment was homogenized and used for quantitative anaerobic culture and a second was frozen and used for real-time PCR-based quantification of P. acnes genomes. P. acnes was identified in 115 cases (40%), coagulase-negative staphylococci in 31 cases (11%) and alpha-hemolytic streptococci in 8 cases (3%). P. acnes counts ranged from 100 to 9000 CFU/ml with a median of 400 CFU/ml. The prevalence of intervertebral discs with abundant P. acnes (≥ 1x103 CFU/ml) was 11% (39 cases). There was significant correlation between the bacterial counts obtained by culture and the number of P. acnes genomes detected by real-time PCR (r = 0.4363, p<0.0001). CONCLUSIONS: In a large series of patients, the prevalence of discs with abundant P. acnes was 11%. We believe, disc tissue homogenization releases P. acnes from the biofilm so that they can then potentially be cultured, reducing the rate of false-negative cultures. Further, quantification study revealing significant bioburden based on both culture and real-time PCR minimize the likelihood that observed findings are due to contamination and supports the hypothesis P. acnes acts as a pathogen in these cases of degenerative disc disease.

1st Department of Pathological Anatomy St Anne's University Hospital Masaryk University Brno Czech Republic

Celgene Corporation Information Knowledge and Utilization San Francisco CA United States of America

Center for Genomic Sciences Drexel University College of Medicine Philadelphia Pennsylvania United States of America

Department of Anesthesia The Johns Hopkins Hospital Baltimore MD United States of America

Department of Microbiology and Immunology Drexel University College of Medicine Philadelphia Pennsylvania United States of America

Department of Microbiology Faculty of Medicine Masaryk university St Anne's Faculty Hospital Brno Czech Republic

Department of Molecular Oncology Central European Institute of Technology Masaryk University Brno Czech Republic

Department of Neurosurgery St Anne's University Hospital Masaryk University Brno Czech Republic

Department of Neurosurgery The Johns Hopkins Hospital Baltimore MD United States of America

Department of Neurosurgery The Warren Alpert Medical School of Brown University Rhode Island Hospital Providence RI United States of America

Department of Neurosurgery University Hospital Brno Masaryk University Brno Czech Republic

Department of Neurosurgery University Hospital Ostrava Ostrava University Ostrava Czech Republic

Department of Orthopedic Surgery OrthoIndy Hospital Indianapolis IN United States of America

Department of Orthopedic Surgery Stanford University Medical Center Stanford University Stanford CA United States of America

Department of Orthopedics Physical Medicine and Rehabilitation University of Munich Munich Germany

Department of Otolaryngology Head and Neck Surgery Drexel University College of Medicine Philadelphia Pennsylvania United States of America and Institute of Molecular Medicine and Infectious Disease Drexel University College of Medicine Philadelphia PA United States of America

Department of Pathology Microbiology and Immunology Vanderbilt University School of Medicine Nashville TN United States of America

Laboratory of Bacterial Pathogenesis and Immunology Rockefeller University New York NY United States of America

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