A Case Study of Rat Bite Fever Caused by Streptobacillus moniliformis

We report a case of rat bite fever, diagnosed based on positive cultures of Streptobacillus moniliformis from blood and synovial fluid. The patient was a 45-year-old man who presented with history of a rat bite and alcoholic liver cirrhosis. He had been bitten on his third finger by a rat, which was caught in a mousetrap installed in his house. Over the course of approximately 2 weeks after the bite, the patient developed fever, rash, and arthralgia. The patient was admitted to our hospital and treated with a combination of ampicillin-sulbactam, vancomycin (VAN), and minocycline (MIN) antibiotics. Initial culture findings from the Anaerobic/F resin blood culture were positive for gram-negative bacillus after overnight incubation. Thus, S. moniliformis infection was suspected, and administration of VAN and MIN was ceased. On hospital day 8, the treatment was switched to oral amoxicillin-clavulanic acid, and the patient was discharged from the hospital. Subsequently, the pathogen was also detected in synovial fluid and identified as S. moniliformis using 16S rRNA sequencing analysis.