Comparative Evaluation of LAMP and Nested PCR for the Rapid Diagnosis of Mycobacterium marinum Infection

PURPOSE: Culture of Mycobacterium marinum is very time-consuming, taking several weeks to produce positive results. Seeking rapid and sensitive diagnostic methods for diagnosis can greatly improve patient treatment. Our study aimed to compare the rapid diagnostic abilities of polymerase chain reaction (PCR), nested PCR and loop mediated isothermal amplification (LAMP) of detecting M. marinum in skin samples from patients with M. marinum infection. METHODS: A total of 6 M. marinum strains and 6 skin samples with definite diagnosis of M. marinum infection were included in the study. We optimized LAMP performance for detection of M. marinum genomic DNA and confirmed the specificity of the primers. Then, the sensitivity of the LAMP and nested PCR assays were assessed by M. marinum strains and clinical samples. RESULTS: Nested PCR was 10-fold more sensitive than the LAMP assay by serial dilution of M. marinum DNA. PCR positive samples were all positive by LAMP detection of 6 clinical M. marinum strains. Out of 6 clinical skin specimens confirmed as M. marinum infection, 0 (0%), 3 (50%), 3 (50%), and 4 (66.6%) were positive by PCR, nested PCR, LAMP and culture. The LAMP shared the same sensitivity than nested PCR in M. marinum strains and clinical samples, but it was easy to perform and faster than nested PCR assay. CONCLUSION: Compared with conventional PCR, LAMP and nested PCR are more sensitive and have a higher detection rate of M. marinum in clinical skin specimens. The LAMP assay proved to be more suitable for rapid diagnosis of M. marinum infection in a shorter time, especially in resource-limited settings.