A Rare Case of Periprosthetic Streptobacillosis - Rapid Identification via Nanopore Sequencing After Inconclusive VITEK MS Results

Background: Streptobacillus moniliformis is the main cause of human streptobacillosis, also known as rat-bite or Haverhill fever. Generally transferred by bites or scratches of rats and other rodents or by rat-excrement polluted water, symptoms commonly start to appear after < 10 days and are highly variable. Due to scarcity, non-specific symptoms, and difficulties in cultivating this fastidious organism, the correct diagnosis is frequently delayed.CaseHere, we report an 85-year old male with a left-sided prosthetic hip joint hospitalized because of immobilizing left hip pain. The patient denied fever, chills, and night sweats. There was no swelling or erythema. Via sonography an echo-free round mass was detected at the left hip. Punctuation of the hip joint revealed putrid secretion. From the synovial fluid and from concomitantly drawn blood cultures grew a pleomorphic, gram-negative rod after 48 h and 35 h, respectively. The microorganism formed small, grey, round, and convex colonies. VITEK and VITEK MS (MALDI-TOF) analysis brought no results. Therefore the unknown isolate was sent to the Institute for Infectious Diseases and Infection Control for sequencing. Following isolation, the DNA was sequenced using Nanopore Third-Generation Sequencing . After one hour enough data were generated to identify the microorganism as Streptobacillus moniliformis .ConclusionTo date, this is the second published case of a periprosthetic bone infection caused by Streptobacillus moniliformis. Although streptobacillosis has a mortality rate of around 10% in humans, it is rarely diagnosed and published. In this context, nanopore sequencing enables fast and reliable diagnostic results for identifying microorganisms and their properties.