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bioRxiv · 10.64898/2026.08.24.746599

Confocal and Transmission electron microscopy imaging of Orientia tsutsugamushi

Rana, M.·Mitra, S.·Hanumanthappa, M. K.·Sharma, N.·Biswal, M.
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Abstract

Scrub typhus, caused by Orientia tsutsugamushi, is an obligate intracellular gram-negative pathogen that remains a cause of acute febrile illness in India. Culture isolation of Orientia tsutsugamushi clinical isolates is infrequent because it is technically more challenging than PCR-based molecular identification. In this report, we describe the culture isolation of Orientia from the whole blood of a 64-year-old farmer with acute febrile illness. Whole blood was inoculated onto an 80% confluent L929 cell line. Real-time PCR targeting the 47-kDa and 56-kDa genes, combined with Sanger sequencing, confirmed the isolate. Transmission electron microscopy of infected L929 cells revealed multiple oval-shaped bacteria within the host cytoplasm. Confocal microscopy demonstrated progressive accumulation of CFSE-labelled bacteria within infected cells over time. These findings support the successful isolation and visualization of a blood-derived O. tsutsugamushi isolate and provide a platform for downstream assays of host-pathogen interactions, antimicrobial susceptibility testing, and vaccine development.

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Rana, M., Mitra, S., Hanumanthappa, M. K., Sharma, N., Biswal, M.. 2026-08-24. Confocal and Transmission electron microscopy imaging of Orientia tsutsugamushi. https://doi.org/10.64898/2026.08.24.746599

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