Use of eschar for the molecular diagnosis and genotypic characterisation of Orientia tsutsugamushi causing scrub typhus

Scrub typhuscaused by Orientia tsutsugamushipresents as an acute febrile illness with a varied presentation from mild illness to fatal disease in the absence of appropriate antibiotic treatment. Performing polymerase chain reaction (PCR) on escharsample acts a rapid diagnostic tool in the early stage of scrub typhuswhen blood is negative. A total of eight patients from whom both whole bloodand escharsamples were collected and tested by nested PCR targeting 56 kDa trichostatinA (TSA) gene to detect O. tsutsugamushi DNA. All (100%) escharsamples and three whole bloodsamples tested positive. Genetic analysisof the 56 kDa TSA gene sequences showed that the majority were related to Karp reference strains, while one clustered with Kawasaki strain. When present, escharshould be favoured as a diagnostic sample over whole bloodin the early phase of infection.