• Shanmuganathan Rajasekaran, Dilip Chand Raja Soundararajan, Chitraa Tangavel, Raveendran Muthurajan, K S Sri Vijay Anand, Monica Steffi Matchado, Sharon Miracle Nayagam, Ajoy Prasad Shetty, Rishi Mugesh Kanna, and K Dharmalingam.
• Department of Spine Surgery, Ganga Hospital, 313, Mettupalayam Road, Coimbatore, India. rajasekaran.orth@gmail.com.
• Eur Spine J. 2020 Jul 1; 29 (7): 1621-1640.

BackgroundTo document the role of sub-clinical infections in disc disorders and investigate the existence of microbiome in intervertebral discs (IVD).MethodsGenomic DNA from 24 lumbar IVDs [8-MRI normal discs (ND) from brain dead yet alive organ donors, 8-disc herniation (DH), 8-disc degeneration (DD)] was subjected to 16SrRNA sequencing for profiling the diversity of human disc microbiome in health and disease. The disc microbiome was further compared to established human gut and skin microbiomes.ResultsAll healthy MRI normal discs from brain dead yet alive organ donors also had a rich bacterial presence. A total of 424 different species (355-ND, 346-DD, and 322-DH) were detected, with 42.75% OTUs being classified at kingdom level, 44% at the phylum level, 22.62% at genus level, and 5.5% at species level. Varying biodiversity and abundance between healthy and diseased discs were documented with protective bacteria being abundant in normal discs, and putative pathogens abundant in DD and DH. Propionibacterium acnes had a similar but lower abundance to other pathogens in all three groups ND (3.07%), DD (3.88%), DH (1.56%). Fifty-eight bacteria were common between gut and IVD microbiomes, 29 between skin and IVD microbiomes, and six common to gut/skin/IVD.ConclusionOur study challenges the hitherto concept of sterility in healthy IVD and documented a microbiome even in MRI normal healthy discs. The varying abundance of bacteria between ND, DD, and DH documents 'dysbiosis' as a possible etiology of DD. Many known pathogens were identified in greater abundance than Propionibacterium acnes, and there was evidence for the presence of the gut/skin/spine microbiome axis.

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