Morphologically variable bacilli of cat scratch disease are identified by immunocytochemical labeling with antibodies to Rochalimaea henselae.

The identification of the causative organisms of cat scratch disease (CSD) has been elusive. The demonstration of Warthin-Starry stain-positive pleomorphic bacilli in lymph nodes of patients with CSD and recent serologic and epidemiologic data suggest an etiologic role of Rochalimaea henselae in CSD. The authors studied lymph node biopsy specimens of 46 patients with illnesses clinically consistent with CSD and found pleomorphic bacilli in 15 (33%). The organisms were labeled by polyclonal rabbit antibodies induced by outer surface proteins of R henselae. This finding further supports the possibility of an important role of R henselae in the pathogenesis of CSD.