Development of Lyophilized Loop-Mediated Isothermal Amplification Reagents for the Detection of Leptospira.

Leptospirosis is considered to be the most widespread zoonosis. This worldwide emerging infectious disease is caused by the pathogenic species belonging to the genus Leptospira. Polymerase chain reaction (PCR)-based diagnostic assays have been developed for detecting Leptospira DNA in cell cultures and clinical samples. Because PCR requires specialized equipment and extensive end-user training, it is not suitable for routine work in resource-limited areas. We have developed a loop-mediated isothermal amplification (LAMP) assay to detect the presence of Leptospira in patient, animal and environmental samples using lyophilized reagents at a single temperature of around 63°C with a heating block. The sensitivity of this LAMP assay is very similar to the PCR method. The amplified DNA products can be visualized with the naked eyes using hydroxy naphthol blue or detected by the fluorescence signal of SYBR green dye in the reaction when an ultraviolet lamp or compact fluorescence tube scanner is used. This LAMP assay is simple, rapid, and can be performed with a water bath or heating block. The lyophilized LAMP reagents are stable for 3 months when stored at 4°C and 1 month when stored at 25°C, respectively. It is ideal for resource-limited settings where leptospirosis is endemic.