FN1 and bacterial infectious disease with sepsis: Fusobacterium nucleatum (Fn) is an opportunistic pathogenic bacterium causing anaerobic infections, such as periodontitis, tonsillitis, appendicitis, and liver abscess.[1,2] Fn was also the most common species identified in Fusobacterium bacteremia, [3] in which Fn is mainly associated with comorbidities such as cancer.[4]