Improved Diagnostic of Spotted Fevers via Loop-Mediated Isothermal Amplification with One Step Strand Displacement

Abstract

Spotted fever rickettsiosis plagues countries around the world. One of the deadliest of this group, Rickettsia rickettsii, responsible for Rocky Mountain spotted fever, is an emerging tickborne illness in North America. The predominant clinical diagnostic is PCR based but does not work until disease has progressed to a severe phase of infection, at which point the outcome of a full recovery is significantly decreased. An alternative, loop mediated isothermal amplification through one-step strand displacement (LAMP-OSD) assay, was developed to improve diagnostic speed and sensitivity. Synthetic dsDNA genes from the 17 kDa surface antigen precursor (AY281069.1) amplified between fifteen minutes to an hour and were detected to concentrations as low as 102 copies/μL. This RMSF LAMP-OSD assay shows promise to deliver results in just a few hours and the detection limit is potentially 100 times more sensitive than qPCR-based assays.