Streptobacillus moniliformis Bacteremia in a Patient with Reactive Arthritis Without a Bite: A Case Report

Introduction: Clinically, rat bite fever (RBF) is a condition caused by Spirillum minus or Streptobacillus moniliformis infections, following rat or any rodent bite. In the absence of a rat bite, this condition cannot be accurately diagnosed. Here, we report the first case of RBF due to S. moniliformis but without a rat bite in China. Case Presentation: A77-year-oldwomanwith reactive arthritiswasadmitted to the hospitaldueto high fever. Initially,wesuspected reactive arthritis with liver function deterioration. However,weisolated a bacteriumwhichwasconfirmedto be S. moniliformis using Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Subsequently, the patient was given targeted anti-infective treatment, which completely resolved the symptoms. The patient was discharged upon fully recovery. Conclusions: Rat bite fever infection caused by S. moniliformis may occur without actual rodent bite. MALDI-TOF MS may be applied to determine the diagnosis of RBF. Difficulties in pathogen and clinical diagnosis highlight the need for discovering the complete exposure history and a greater understanding of this rare zoonotic infections.