Cat scratch disease: evidence for a bacterial etiology. A retrospective analysis using the Warthin-Starry stain

97 cases of acute necrotizing granulomatous lymphadenitis (so called "reticulozytärabszedierende Lymphadenitis") were examined retrospectively with the Warthin-Starry stain, in order to detect bacteria in patients with cat-scratch disease (CSD). 27 patients with CSD were found and among those, bacteria were demonstrated in 4. The organisms were pleomorphic rods of about 3 micron length and occurred in clumps within foci of fresh necrosis. We found the organisms in a much lower percentage than has been described in the literature. The reasons may be that many of our patients had antimicrobial treatment prior to the biopsy and that step-sectioning of the specimen may be necessary in order to detect fresh lesions. Our findings seem to confirm the observation that CSD may have a bacterial aetiology.