Molecular detection of "Candidatus Rickettsia tarasevichiae" by Loop-mediated Isothermal Amplification (LAMP) of the ompA gene.

"Candidatus Rickettsia tarasevichiae" (CRT) is increasingly being recognized as a disease causative agent in China and poses a great challenge to public health. Rapid and accurate detection is indispensable for laboratory diagnosis of infection caused by CRT and its surveillance in ticks. In the present study, a novel DNA-based loop-mediated isothermal amplification (LAMP) assay targeting the ompA gene was developed for the detection of CRT in tick samples. A set of universal primers specific to CRT were designed using PrimerExplorer V5 software. The analytical sensitivity, evaluated using recombinant plasmids containing the ompA gene, reached up to 1 copy per reaction, greater than that of the PCR assay targeting the same gene. This LAMP assay specifically detected CRT and showed no cross-reaction with other species common in China within the genus Rickettsia. In addition, this newly developed LAMP assay presented high diagnostic sensitivity of CRT detection validated by known positive DNA samples from ticks and simulated clinical samples. The applicability of the LAMP assay was evaluated by screening CRT from ticks, and the result showed that CRT circulation in Weichang County, China, was confirmed. Our findings indicate that this LAMP method is sensitive and specific for the detection of CRT and may have a potential application in the detection of CRT infection in patients and ticks.