Complete Resolution of a Fusobacterium necrophorum Liver Abscess With Short-Course Antibiotics and Drainage.

A pyogenic liver abscess results from bacterial invasion of hepatic parenchyma via hematogenous, biliary, or direct routes. While Enterobacterales predominate, anaerobes such as Fusobacterium necrophorum are rare causes, often missed by conventional cultures due to prior antibiotics and fastidious growth. A 52-year-old man with diabetes, hypertension, and dyslipidemia presented with two weeks history of fever and epigastric pain. Labs showed leukocytosis (WBC: 12.22 × 109/L, neutrophils: 8.91 × 109/L) and CRP of 289 mg/L. A CT scan revealed a ring-enhancing abscess in segment IV measuring 4.9 × 3.5 × 4.9 cm. Drainage yielded 30 mL of pus. Ceftriaxone was started empirically, which was upgraded later to piperacillin-tazobactam. Blood and pus cultures were negative. 16S rRNA sequencing later identified F. necrophorum (99.79% match). He completed eight days of intravenous antibiotics but did not adhere to the prescribed oral antibiotic regimen after discharge. At the five‑month follow‑up, he demonstrated complete clinical and radiological resolution of the liver abscess. This case highlights F. necrophorum as an underdiagnosed cause of pyogenic liver abscess in patients with diabetes. Molecular methods, such as 16S rRNA sequencing, facilitate accurate pathogen detection and guide targeted antimicrobial therapy. In this patient, source control through drainage was sufficient even with a short course of antibiotics, suggesting that treatment duration may be individualized in selected cases.