loop-mediated isothermal amplification test for rapid identification of clinical nocardia isolates

Background: nocardia is a gram-positive and partially acid-fast bacterium. the species are widely distributed in the environment and cause severe human infections. nocardiosis is not easily identifiable due to the lack of pathognomonic clinical signs. objectives: the present study was designed to develop and evaluate a simple and quick method based on a loop-mediated isothermal amplification (lamp) assay for detecting nocardia spp isolated from bronchoalveolar lavage (bal) samples. methods: in this cross-sectional study, 357 bal samples were collected from two teaching hospitals. the polymerase chain reaction (pcr) was performed using a set of species-specific primers for the 16s rrna gene. kinyoun acid-fast staining and culture were done on the sabouraud dextrose plate. the optimal lamp reaction condition was set at 65°c for 45 min, with the recognition limit as 1 pg dna/tube and 100 cfu/reaction. in addition to calcein and manganous ions, agarose gel electrophoresis was used to visualize the amplified lamp products. results: out of 357 bal samples, 0 (0.0%), 4 (1.1%), 9 (2.5%), and 10 (2.8%) nocardia strains were identified by direct staining of partial acid-fast, streak culture plate, pcr, and lamp methods, respectively. conclusions: we developed a new lamp technique for the recognition of nocardia, which is fast, very precise, simple, and low-cost. according to our knowledge, this is the first report of the lamp method to detect nocardia in clinical samples.