This is a case of a 69-year-old obese woman treated with posterior spinal stabilization for lumbar degenerative stenosis who developed delayed and persistent surgical site infection sustained by Bacteriodes fragilis. This microorganism is characterized by slow growth and resistance to antimicrobial agents. The patient underwent a surgical treatment with debridement of the surgical wound without hardware removal. After fourteen months the patient had a recurrence of low back pain, low-grade fever and dehiscence of surgical wound with the need of hardware removal. The intra-operative culture was positive for the same microrganism, than she healed with target antibiotic therapy.