Abstract Background: Surgical site infections (SSIs) following spinal surgery remain a significant concern despite advances in infection control. We report an unexpected outbreak investigation at an institution with historically low infection rates. Methods: During April–June 2012, our spinal surgery department experienced 6 SSIs among 84 procedures (7.1%) compared with our baseline rate of 0.3%. We conducted a comprehensive MECE (Mutually Exclusive and Collectively Exhaustive) analysis, a systematic framework that ensures all potential factors are examined without overlap or omission, investigating all potential bacterial contamination routes: pre-operative, intra-operative, and post-operative factors. Statistical analysis was performed using Fisher exact test. Results: All infections occurred within 8 days post-operatively with skin commensal organisms as causative agents. Patient characteristics were similar between SSI-positive (n = 6) and SSI-negative (n = 78) groups. Environmental investigations revealed no abnormalities. Crucially, all SSI cases involved novice technicians (non-nursing staff responsible for instrument handling) with <6 months experience (100% vs. 10.3%, p < 0.001), all working in a smaller operating room. Conclusions: Traditional risk factor analysis failed to identify the outbreak cause. Only systematic MECE analysis identified a strong association with staff-related factors. Following targeted training interventions, infection rates returned to baseline levels. This investigation demonstrates that even institutions with excellent baseline infection control remain vulnerable to process failures requiring comprehensive systematic investigation beyond conventional risk factors.
OKUMURA et al. (Wed,) studied this question.