Comparison of a conventional and nested PCR for diagnostic confirmation and genotyping of Orientia tsutsugamushi.

[scrub typhus]

A nested polymerase chain reaction (PCR ) targeting the 56 -kDa antigen gene is currently the most commonly used molecular technique for confirmation of scrub typhus and genotyping of Orientia tsutsugamushi . In this study , we have compared the commonly used nested PCR (N-PCR ) with a single -step conventional PCR (C-PCR ) for amplification and genotyping . Eschar samples collected from 24 patients with scrub typhus confirmed by IgM enzyme-linked immunosorbent assay were used for DNA extraction following which amplifications were carried out using nested and C-PCR methods . The amplicons were sequenced and compared to other sequences in the database using BLAST . Conventional PCR showed a high positivity rate of 95 .8 % compared to the 75 % observed using N-PCR . On sequence analysis , the N-PCR amplified region showed more variation among strains than the C-PCR amplified region . The C-PCR , which is more economical , provided faster and better results compared to N-PCR .