Bacteriologic culture of excised intervertebral disc from immunocompetent patients undergoing single level primary lumbar microdiscectomy

Study Design: A consecutive case series from a single center of patients undergoing primary microdiscectomy for lumbar herniated nucleus pulposus (HNP) who received microbiologic laboratory culture of excised disc material. Objective: To determine the prevalence of positive bacterial cultures in the disc material of immunocompetent patients without diabetes mellitus or other immune compromise. Summary of Background Data: The intradiscal space is a physiologically tenuous environment in terms of oxygen tension, pH, and vascularity. This space may be susceptible to indolent infections with an unknown effect on the pathogenesis of HNP. Methods: This case series included 52 patients with radiculopathy and magnetic resonance imaging positive for HNP who elected for lumbar microdiscectomy after failure of conservative management. All patients received primary surgery at a single spinal level in the absence of diabetes mellitus, systemic steroid use, chemotherapy, other immune compromise, or prior lumbar surgery. Excised disc material was sent for routine bacterial culture. No special culture techniques were used to improve the yield of positive cultures. Results: Cultures were positive in 10 patients (19.2%). Propionibacterium acnes was the sole organism isolated in 7 (13.5%), with Peptostreptococcus and Staphylococcus species accounting for the remainder. There were 24 women (46.2%) and 28 men (53.8%) with a mean age of 43.9 years (SE 1.8). Duration of symptoms was greater than 12 weeks in 35 patients (67.3%). Onset of symptoms was insidious in 22 patients (42.3%), sudden in 16 (30.8%), and the history was unclear in the remainder. Prior epidural steroid injection was received by 17 patients (32.7%), and 11 patients had a history of smoking (21.2%). None of these variables was significantly different in patients with positive and negative cultures (P >0.05). Conclusions: P. acnes was isolated by routine laboratory culture of excised disc material in 13.5% of immunocompetent patients undergoing primary single level discectomy for radiculopathy with lumbar HNP; other organisms were isolated in 6% of patients. Level of Evidence: Diagnostic level of evidence III.