First Case in China of Recurrent Liver Abscess Complicated by Bloodstream Infection Caused by Shewanella algae After Surgery for Cholangiocarcinoma: Diagnostic Value of Metagenomic Next-Generation Sequencing

Background: Shewanella algae (S. algae) is an emerging halophilic, facultative anaerobic opportunistic pathogen, with rare reported cases of clinical infection. Here, we present a case of S. algae infection diagnosed with the assistance of plasma metagenomic next-generation sequencing (mNGS). Case Presentation: An elderly man presented with recurrent fever one year after surgery for cholangiocarcinoma and had a medical history of multiple malignancies and prior infections . Imaging examinations revealed an enlarging liver abscess. Multiple sets of blood cultures yielded negative results, and empirical antimicrobial therapy was ineffective or associated with adverse reactions. Plasma mNGS detected S. algae with 231 sequence reads and a relative abundance of 14.56%. Further inquiry into the patient’s history revealed seafood consumption one week before the onset of fever. Based on the mNGS findings, epidemiological characteristics, and imaging results, the patient was ultimately diagnosed with recurrent liver abscess complicated by bloodstream infection caused by S. algae . Following adjustment of antimicrobial therapy according to the etiological diagnosis, inflammatory markers decreased, and the liver abscess showed marked improvement. The patient was subsequently discharged in good general condition. Conclusions: To our knowledge, this study reports the first case in China of recurrent liver abscess complicated by bloodstream infection caused by S. algae in a patient after surgery for cholangiocarcinoma. It is also the first time that mNGS technology has been used to assist in the diagnosis of S. algae infection in such patients. This case suggests that for patients with complex conditions where conventional tests fail to identify the pathogen, the possibility of infection with rare pathogens should be considered. mNGS can overcome the limitations of traditional diagnostic methods, provide evidence for accurate diagnosis, and reduce unnecessary antibiotic exposure and associated adverse reactions in clinical treatment.