A case report of bloodstream infection caused by co-infection of Olsenella uli and Christensenella hongkongensis.

We report a case of a Chinese male patient with a history of Hepatolithiasis who was admitted for abdominal pain, fever, and chills. Imaging studies suggested cholangitis and Hepatolithiasis. Blood cultures revealed two rare fastidious anaerobes-Olsenella uli and Christensenella hongkongensis-confirmed by MALDI-TOF MS and 16S rDNA full-length sequencing. These organisms failed to grow on standard solid media but were successfully isolated using a self-prepared solid medium formulated based on the nutrient solution from blood culture bottles. This suggests that for anaerobic bacteria with positive blood cultures but negative routine cultures, the use of such media may improve isolation rates. This case demonstrates that although such infections are extremely rare, mortality may correlate with the severity of underlying disease. Successful identification provides a reference method for isolating and identifying fastidious bacteria in similar cases.