May Latent Bacterial Infection Provoke Degenerative Disc Disease?

Abstract

Introduction As a chronic condition, the degenerative disc disease is a significant health problem. Several factors, such as genetics, mechanical stress, inflammatory and biochemical changes, vascular aspects, as well as infection may initiate degenerative processes, most commonly affecting the nucleus pulposus. It has been proposed that disc degeneration might be initiated by possible long-lasting low-grade infection. Materials and Methods The aim of the study was to assess the incidence of bacterial infection in the lumbar intervertebral disc specimens obtained from patients with disc herniation. In a prospective study, 62 patients were included (49% women and 51% men, average age 56 years, range 22–83 years). No experience of previous invasive spinal diagnostic procedures was reported. Disc specimens from levels L1 to S1 were collected during discectomies and microbiologically tested on blood, thioglycolate, and nutrient agars. MRI and CT were used as diagnostic methods and comparison of microbiological results to clinical signs and imaging was done. Results In included patients, affected discs were removed. All microbiological cultures of disc specimens remained sterile after 1 week. Clinically, no signs of discitis were observed. The absence of an acute infection was confirmed by routine laboratory tests. Although clinical signs corresponded well to the MRI and CT imaging results, no connection with microbiological tests was found. Conclusion The exact pathobiology of degenerative disc disease is unknown. According to some studies, intradiscal bacteria may initiate a low-grade infection, playing a role in intervertebral disc degeneration. Our observations do not support this fact. Microbiological samples remained sterile in all patients, meaning that intervertebral disc is a sterile environment and bacterial infection is unlikely the cause of degeneration. Positive disc cultures in other studies may have resulted from specimen contamination after disc removal. However, the hypothesis of disc infection cannot completely be excluded because of slow growing and special growth conditions requiring bacteria that were not tested in our study. The potential role of low-grade bacterial infection contributing to the pathogenesis of degenerative disc disease thus remains uncertain. The genesis of disc degeneration might originate in the immune system and repeated episodes of injury and reparation that could culminate to progressive tissue damage.