A loop-mediated isothermal amplification (LAMP) assay was developed for rapid, specific and sensitive detection of Renibacterium salmoninarum in 1 h without thermal cycling. A fragment of R. salmoninarum p57 gene was amplified at 63 degrees C in the presence of Bst polymerase and a specially designed primer mixture. The specificity of the BKD-LAMP assay was demonstrated by the absence of any cross reaction with other bacterial strains, followed by restriction digestion of the amplified products. Detections of BKD-LAMP amplicons by visual inspection, agrose gel electrophoresis, and real-time monitoring using a turbidimeter were equivalently sensitive. The BKD-LAMP assay has the sensitivity of the nested PCR method, and 10 times the sensitivity of one-round PCR assay. The lower detection limit of BKD-LAMP and nested PCR is 1 pg genomic R. salmoninarum DNA, compared to 10 pg genomic R. salmoninarum DNA for one-round PCR assay. In comparison to other available diagnostic methods, the BKD-LAMP assay is rapid, simple, sensitive, specific, and cost effective with a high potential for field application.Dis Aquat Organ. 2008 Aug 2781(2):143-51.Saleh M, Soliman H, El-Matbouli M.SourceClinic for Fish and Reptiles, Faculty of Veterinary Medicine, Kaulbachstr. 37, University of Munich, 80539 Munich, Germany.