Development of a serologic test for cat scratch disease (CSD) and evidence to support that Rochalimaea henselae is a causative agent of CSD in Australia

Abstract

An indirect immunofluorescence antibody (IFA) test was developed to assist in the diagnosis of suspected cases of cat scratch disease (CSD). The IFA test was developed using <i>Rochaliamaea henselae</i> infected bovine endothelial cells. The IFA test was shown to give comparable antibody titres to a similar assay used by CDC in Atlanta. Using control sera from patients with no detectable antibodies to <i>H. pylori</i> the IFA test had a specificity of 98% at the cut-off titre of 1:64. Of 73 serum samples subsequently sent for testing for antibodies to <i>Rhenseiae</i>, 9 were positive in the IFA test. Eight of the positives had regional adenitis and one had Parmaud's oculoglandular syndrome. Two of the eight positives had no contact with a cat in the three months prior to presenting with symptoms. Five of the positives had a fine needle aspirate of a lymph node or lymph node biopsy with histology showing nonspecific inflammation and 4 of these had granulomatous changes. Two patients with a clinical history of CSD had a titre of <1:64. Oligonucleotide primers used for amplification of 16S rDNA of <i>Rochalimaea</i> sp were used to detect the organisms in tissue from a CSD patient. Using these primers a 300 bp product was obtained in lymph node aspirates of a patient with CSD similar to that obtained with the <i>R.henselae</i> control organism. In addition, organisms isolated from blood and fleas of the patient's cat also produced a 300 bp product in the PCR assay. Danilla Grando at St. Vincent's in Melbourne forwarded an isolate from a conjunctival ulcer of a patient with oculoglandular syndrome. This patient had a serum titre of 1:512 in the IFA test and the isolate was positive in the PCR assay. The organisms isolated from the blood and fleas of the CSD patient's cat and the clinical isolate have been preliminarily characterised as <i>R. henselae</i> by testing in the Rapid ID ANA II test.