Metagenomic Next-Generation Sequencing Reveals Co-Infection with Legionella pneumophila and Anaerobic Bacteria in a Patient with Severe Pneumonia and Lemierre's Syndrome: A Case Report

Background: Legionella pneumonia is one of the most severe types of atypical pneumonia, impairing multiple organ systems, posing a threat to life. Diagnosing Legionella pneumonia is challenging due to difficulties in culturing the bacteria and limitations in immunoassay sensitivity and specificity. Case presentation: This paper reports a rare case of sepsis caused by combined infection with Legionella pneumophila and Fusobacterium necrophorum , leading to respiratory failure, acute kidney injury, acute liver injury, myocardial damage, and electrolyte disorders. In addition, we systematically reviewed literature on patients with combined Legionella infections, analyzing their clinical features, laboratory results and diagnosis. Conclusions: For rare pathogens that cannot be identified by routine laboratory tests, metagenomic next-generation sequencing (mNGS) can be a powerful supplement to pathogen screening and plays a significant role in the auxiliary diagnosis of complex infectious diseases.