Comparison of nested polymerase chain reaction and real-time polymerase chain reaction targeting 47kda gene for the diagnosis of scrub typhus

Abstract

Introduction: Scrub typhus is a zoonotic infection caused by Orientia tsutsugamushi which is transmitted by Leptotrombidium mites. The disease manifests as a mild-to-severe illness with non-specific clinical symptoms. Rapid diagnosis and prompt treatment are essential for patient management. Both serological and molecular methods are used for the diagnosis of scrub typhus. The present study assessed the usefulness of detection of the gene encoding the 47kDa outer-membrane protein (OMP) for the laboratory diagnosis of scrub typhus. Materials and Methods: Nested polymerase chain reaction (nPCR) and real-time PCR targeting 47 kDa OMP antigen gene of O. tsutsugamushi were performed on ethylenediaminetetraacetic acid blood samples. Results: Six of the 103 (5.8%) patients showed the presence of 47kDa gene by nPCR. Seventy of 103 (67.9%) cases showed the presence of 47kDa gene by qPCR. Among the 70 positive cases, the majority of them were females (40/70, 57.1%). The highest number of positive cases was observed during October–February. Conclusion: Real-time PCR targeting O. tsutsugamushi-specific 47-kDa gene is more sensitive than nPCR and may be the assay of choice for the detection of the organism in patients with suspected scrub typhus.