Usefulness of Eschar PCR for Diagnosis of Scrub Typhus

ABSTRACT

BACKGROUND: We describe a case of scrub typhus, of which the diagnosis was made by PCR using eschar and serologic diagnosis. The patient's attendant insisted that the eschar like crust lesion was caused by minor trauma. In order to find out whether the crust on his head is eschar or not, PCR using eschar was performed. MATERIALS AND METHODS: Informed consent was taken, and then a piece of crust was taken apart. We immerged the crust with about 1 mL of saline bottle. We performed the nested PCR of gene that encodes the 56-kDa specific protein for O. tsutsugamushi. The first serology test for O. tsutsugamushi using indirect immunofluorescent antibody was performed. Then the second serology test & eschar PCR assay were performed at the second week after treatment. RESULTS: 56-kDa protein specific bands were detected in both buffy coat and eschar sample collected at first day of antibiotic administration. However, in the follow up PCR study 7 days after antibiotics administration, 56-kDa protein specific band was detected at only newly formed eschar, not at buffy coat. CONCLUSION: The eschar PCR assay can be useful diagnostic test, even though patient with scrub typhus underwent appropriate antibiotics therapy. The nested PCR method for eschar might be both rapid diagnostic test for scrub typhus in the early acute stage and differential test whether a crust is eschar or not.