A colorimetric detection system for Calymmatobacterium granulomatis.

ABSTRACT

OBJECTIVE: To incorporate the first polymerase chain reaction (PCR) assay for Calymmatobacterium granulomatis into a colorimetric detection system for use in routine diagnostic laboratories. METHODS: A capture oligonucleotide specific for the Klebsiella phoE gene was covalently linked to tosyl activated magnetic beads. Biotinylated phoE PCR products obtained from 14 positive specimens from patients with donovanosis and isolates of Klebsiella pneumoniae, K rhinoscleromatis, and K ozaenae were cleaved with HaeIII for the purpose of differentiation, captured by the prepared beads, and subjected to standard EIA detection methodology. Eight samples from unrelated genital conditions underwent the same procedure. It was anticipated from the sequence data that the biotinylated fragment would be cleaved from the capture oligonucleotide target region in the three Klebsiella phoE products (that is, a negative colorimetric result) while the entire fragment of interest would remain intact in the positive C granulomatis phoE products (that is, a positive colorimetric result). RESULTS: All 14 positive specimens from patients with donovanosis gave strong colorimetric readings with this detection system. Isolates of K pneumoniae, K rhinoscleromatis, K ozaenae, and the eight specimens from unrelated genital conditions were negative. CONCLUSION: The successful development of a colorimetric detection system for C granulomatis incorporating two levels of specificity enables the molecular diagnosis of this condition to be undertaken by routine diagnostic laboratories. This should have an important role in the Australian government's campaign to eradicate donovanosis by 2003 though the test still needs to undergo trials and be validated using a larger number of samples from geographically diverse parts of the world in order to ascertain the generalisability of the methodology.