Letter to the Editor concerning “Prospective study using anterior approach did not show association between Modic 1 changes and low grade infection in lumbar spine” by Rigal J, et al.: Eur Spine J; 2016 Apr; 25(4):1000–5

Excerpt

The association between lumbar disc degeneration and chronic infection of the intervertebral disc remains controversial. There is some evidence for a relationship between the presence of bacteria and both low back pain with disc herniation and Modic Type 1 change associated with disc herniation and for causation [1]. However, further work is needed to determine whether the isolation of organisms from intervertebral discs is a result of intraoperative contamination or represents low-grade infection of the spine which contributes to chronic low back pain. Using an anterior video-assisted approach, allowing biopsy without skin contact, Rigal et al. [2] recovered very low numbers of organisms from disc tissue samples (6 from 313, 2 %). They concluded that the organisms recovered are most likely the result of contamination from the skin during the surgical removal of tissue. We challenge this interpretation on the basis that the culture conditions employed in their study would not support the recovery of all anaerobic organisms present, including many Propionibacterium acnes, which has been recovered in studies by other groups, including our own [3‐5]. Rigal et al. [2] state that they cultured the disc fragments in a brain–heart type culture medium and incubated at 37 °C in an atmosphere enriched with 5 % CO₂ for 15 days. Whilst P. acnes is aerotolerant, it requires strict anaerobic culture conditions for efficient recovery and growth from clinical samples. In our studies, we cultured five replicate fragments of disc tissue from each of 61 patients on blood agar plates incubated under strict anaerobic conditions and five replicate fragments of disc tissue on blood agar under aerobic conditions in an atmosphere enriched with 5 % CO₂ [5]. We obtained positive cultures in tissues from 26/61 (43 %) patients under anaerobic growth conditions but only 6/61 (10 %) under aerobic conditions. P. acnes was the predominant organism recovered under anaerobic conditions (22/26, 85 % of the positive anaerobic cultures). Significantly, in every case, where this organism was cultured anaerobically, it was not cultured from the duplicate tissue samples incubated under aerobic conditions. We believe that the low numbers of positive cultures observed in the study by Rigal et al. cannot be interpreted as the absence of organisms from the disc tissues and evidence for contamination of tissues by other workers. Further studies using appropriate culture conditions with stringent conditions to minimise risk of tissue contamination are needed to help determine whether low-grade infection caused by P. acnes plays a role in low back pain associated with Modic type 1 changes. …