S. turonicum Caused Bacteremia and Knee Arthritis in an Immunocompromised Patient

A 61-year-old woman with multiple myeloma and severe hypogammaglobulinemia while receiving teclistamab presented with fever and a painful, inflamed knee. Blood and joint-fluid cultures grew tiny spiral-shaped gram-negative bacteria, but matrix-assisted laser desorption/ionization time-of-flight mass spectrometry did not identify them. The patient also developed transient annular erythema on her trunk and limbs. The report is a single-patient case from southeast France in 2025.

Sequencing of the 16S rRNA gene from joint fluid identified Spiroplasma turonicum, a bacterium generally associated with plants, insects and ticks. The patient’s symptoms persisted after empirical carbapenem treatment and two arthroscopic procedures. After doxycycline and levofloxacin were started, inflammatory markers and local signs improved. She completed six weeks of antibiotics and had no clinical relapse at four-month follow-up.

The authors report arthritis with systemic S. turonicum infection in a severely immunocompromised patient; human infections with this species are rare. They note that specialized molecular testing may be needed when routine identification methods fail. The findings come from one case and cannot establish typical presentation, treatment effectiveness or risk. The article is an early-release publication, and the authors’ proposed link between the skin findings and infection remains speculative.