Quantification of Propionic Acid in the Bovine Spinal Disk after Infection of the Tissue with P. Acnes Bacteria.

STUDY DESIGN Research OBJECTIVE.: The goal of this study was to investigate whether P. acnes infection of the intervertebral disc can be detected noninvasively by NMR spectroscopy. SUMMARY OF BACKGROUND DATA Microbiological studies of surgical samples suggest that a significant subpopulation of back pain patients may have occult disc infection with P. acnes bacteria. This hypothesis is further supported by a double-blind clinical trial showing that back pain patients with Modic type 1 changes may respond to antibiotic treatment. Because significant side effects are associated with antibiotic treatment, there is a need for a noninvasive method to detect whether specific discs in back pain patients are infected with P. acnes bacteria. METHODS P. acnes bacteria were obtained from human patients. NMR detection of a propionic acid in the bacteria extracts was conducted on 500 MHz high-resolution spectrometer while in vivo NMR spectroscopy of an isolated bovine disk tissue infected with P. acnes was conducted on 7T MRI scanner. RESULTS NMR spectra of P. acnes metabolites revealed a distinct NMR signal with identical chemical shits (1.05 and 2.18 ppm) as propionic acid (a primary P. acne metabolite). The 1.05 ppm signal does not overlap with other bacteria metabolites, and its intensity increases linearly with P. acnes concentration. Bovine disks injected with P. acnes bacteria revealed a very distinct NMR signal at 1.05 ppm, which linearly increased with P. acnes concentration. CONCLUSIONS The 1.05 ppm NMR signal from propionic acid can be used as a marker of P. acnes infection of discs. This signal does not overlap with other disc metabolites and linearly depends on P. acnes concentration. Consequently, NMR spectroscopy may provide a non-invasively method to detect disc infection in the clinical setting. LEVEL OF EVIDENCE N/A.