Yersinia pseudotuberculosis: an unexpected cause of fever and a hot joint

Yersinia pseudotuberculosis is a Gram-negative zoonosis which occasionally infects humans via ingestion of contaminated food and water, and typically causes a self-limiting gastrointestinal tract infection. Patients who are immunocompromised, have haemochromatosis or liver cirrhosis are more likely to develop serious complications such as bacteraemia. We present the case of a 76-year-old man with fever and an acutely tender, swollen right knee. Blood cultures were positive for Y. pseudotuberculosis, and 16s ribosomal PCR analysis of his knee aspirate confirmed septic arthritis. He was treated with intravenous ceftriaxone and made an excellent recovery following knee washout. Interestingly, our patient did not have any of the classic risk factors described in the literature, or history of exposure to the pathogen to explain his diagnosis. To our knowledge, this is only the second confirmed case of Y. pseudotuberculosis bacteraemia with septic arthritis, and the first to involve the knee joint.