Answer to the letter to the editor of M.N. Capoor et al. concerning “Ribosomal PCR assay of excised intervertebral discs from patients undergoing single-level primary lumbar microdiscectomy’’ by Alamin TF, Munoz M, Zagel A, et al.: Eur Spine J; 2017

Excerpt

We agree with the assertion that the possibility of disc infection as an instigator in the pathophysiologic process of symptomatic disc degeneration is both an intriguing hypothesis, but also one that is important to critically assess because of its clear implications for treatment. In our study, with stringent technique, we found none of the 44 disc specimens obtained from surgical microdiscectomy that tested positive for the presence of bacterial 16S rRNA on RT-PCR. A careful read of the studies referenced in the above letter will reveal that these studies contained no negative internal controls while using a technique that is susceptible to yielding false-positive results, and further because of the high rate of specimens in Capoor et al. 2016, that had some level of detectable P. acnes genomic material (in fact, in only 4% of specimens were P. acnes genomes undetectable by their methods). A positive correlation was found in these studies between the presence of > 1 × 10³ cfu’s (an arbitrarily defined number) on culture for P. acnes and the number of genomes detectable by their methods. Without the presence of a negative surgical control, it is difficult to know how to evaluate the specificity of these findings. …