Subclinical Propionibacterium Acnes Infection Estimation in the Intervertebral Disc (SPInE-ID): a Prospective Cohort

INTRODUCTION Low back pain is a frequent condition in the population, as well as vertebral endplates abnormalities, described by Modic et al.(1,2), that affect up to 6% of the general population, and, up to 46% of patients with low back pain(3). Modic type I changes are described as vertebral bone marrow edema related to acute low back pain(4). When Modic changes are detected, chances of one presenting unspecific low back pain are 4.5 times higher(1,2).

Subclinical infection caused by low-virulence pathogen can possibly lead to vertebral endplate abnormalities, detected in magnetic resonance imaging (MRI) studies, and differentiation between infection and Modic changes may be difficult(5,6). Subclinical infection can also be associated with increasing low back pain(7). Albert et al(8) reported 61 patients who had undergone surgical treatment for lumbar disc herniation where 46% of cases had a positive culture. The same authors also reported that 80% of patients with a positive culture for anaerobic pathogens presented Modic type I changes at the adjacent vertebra after a two-year follow-up, against 44% of patients with negative culture. Some studies demonstrated the presence of low-virulence pathogens in intervertebral disc tissue cultures(6-10), most commonly reported to Propionibacterium acnes.

Chronic low back pain and Modic type I changes have been treated with antibiotics for up to 100 days with superior outcomes compared to sham treatment(7). Patients were treated with amoxicillin/clavulanate (500mg/125mg)(7) based on the study where sciatica is associated with Propionibacterium acnes(8).

However, Carricajo et al(11) suggest that the presence of P. acnes in the intervertebral discs is due to either external surgical or laboratory contamination. These authors detected positive disc culture in only 3.7% of cases out of 54 patients. Furthermore, same authors demonstrated that samples of spinal muscle and ligamentum flavum collected intraoperatively at the end of procedure had positive cultures in 14.8% of cases with a negative disc culture.

A systematic review performed by Urquhart et al(12) concluded, that there is moderate evidence that a relationship between positive culture with Modic type I changes and low back pain exists, although there was low evidence for relationship of cause. For that, authors concluded that new studies should be made to determine whether pathogens in the disc are originated from external contamination or if they are truly involved in the development of chronic back pain.