[Listeria arthritis in chronic polyarthritis during low dose prednisolone and methotrexate therapy. Case report and review of the literature].

We report about a patient with polyarticular rheumatoid arthritis taking methotrexat and 5 mg prednisolone who developed in the course of a RA flare a septic arthritis in the right shoulder. Listeria monocytogenes could be identified as the causative bacteria. Clinically, the Listeria-induced septic arthritis could not be differentiated from rheumatoid arthritis; fever was not present. The synovial analysis showed a granulocytic effusion with 19,000 cells/ml; there was no microbiological growth within the first 24 hours. Only the low glucose level indicated a possible septic arthritis. After 48 hours, gram-positive bacterial growth was evident and Listeria monocytogenes could be isolated after 72 hours. Therapy was initiated by antibiotic treatment and arthrotomy with synovectomy followed by extensive irrigation which proved effective in bacterial elimination but joint destruction resulted. During the whole course, Listeria antibodies were negative and proved to be too insensitive. The incidence of Listeria-induced arthritis is very low; a review of the literature revealed only 24 reported cases. It occurs primarily in patients with rheumatic diseases under immunosuppression and in prosthetic joints. The diagnosis is based on cultural detection. It is important to cultivate synovial effusions for longer than 24 hours in order to identify Listeria. This is of relevance since Listeria serology is not sensitive.