LAMP-based method for a rapid identification of Legionella spp. and Legionella pneumophila

Legionella pneumophila is accounted for more than 80% of Legionella infection. However it is difficult to discriminate between the L. pneumophila and non-L. pneumophila species rapidly. In order to detect the Legionella spp. and distinguish L. pneumophila from Legionella spp., a real-time loop-mediated isothermal amplification (LAMP) platform that targets a specific sequence of the 16S rRNA gene was developed. LS-LAMP amplifies the fragment of the 16S rRNA gene to detect all species of Legionella genus. A specific sequence appears at the 16S rRNA gene of L. pneumophila, while non-L. pneumophila strains have a variable sequence in this site, which can be recognized by the primer of LP-LAMP. In the present study, 61 reference strains were used for the method verification. We found that the specificity was 100% for both LS-LAMP and LP-LAMP, and the sensitivity of LAMP assay for L. pneumophila detection was between 52 and 5.2 copies per reaction. In the environmental water samples detection, a total of 107 water samples were identified by the method. The culture and serological test were used as reference methods. The specificity of LS-LAMP and LP-LAMP for the samples detection were 91.59% (98/107) and 93.33% (56/60), respectively. The sensitivity of LS-LAMP and LP-LAMP were 100% (51/51) and 100% (18/18). The results suggest that real-time LAMP, as a new assay, provides a specific and sensitive method for rapid detection and differentiation of Legionella spp. and L. pneumophila and should be utilized to test environmental water samples for increased rates of detection.