Specific and rapid detection of foodborne Salmonella by loop-mediated isothermal amplification method

Rapid Detection of Viable Salmonellae in Produce by Coupling Propidium Monoazide with Loop-Mediated Isothermal Amplification

“…Previously, invA-based molecular detection assays using multiple platforms such as PCR, qPCR, and LAMP have been designed to accurately detect Salmonella with a broad specificity for more than 100 Salmonella serovars while demonstrating excellent exclusivity for non-Salmonella strains (8,15,36,45). Findings of this study corroborated with these previous reports on the high specificity of invA-based molecular detection assays for Salmonella.…”

“…A closer examination of primer sequences in this study and previously published invA-based LAMP studies (15,20,45) showed that the region (5Ј end of F3 and 3Ј end of B3) covered by our primers (503 to 682 bp) and those of Hara-Kudo et al (225 to 468 bp) (15) overlapped with that (371 to 655 bp) targeted by the widely used Salmonella invA PCR primers (36). Primers reported in the other two studies (20,45) were essentially the same with only one nucleotide deletion at the 3Ј end of each FIP and BIP primer in the EMA-LAMP study (20), and the region (672 to 912 bp) covered was downstream of the invA PCR primers without any overlap. In addition, two loop primers were each incorporated in this study and the study by Hara-Kudo et al (15), while the other two studies had no loop primers (20,45).…”

“…This level of sensitivity was comparable to that of qPCR but up to 100-fold more sensitive than that of PCR run in parallel. The first published invA-based LAMP for Salmonella detection had a sensitivity of 2.2 CFU/test tube (15), whereas a more recent one reported a detection limit of 100 fg DNA/ tube (45), approximately 20 CFU/tube (23). In both studies, LAMP was found to be 10-fold more sensitive than PCR for all serotypes tested (15,45).…”

“…Primers reported in the other two studies (20,45) were essentially the same with only one nucleotide deletion at the 3Ј end of each FIP and BIP primer in the EMA-LAMP study (20), and the region (672 to 912 bp) covered was downstream of the invA PCR primers without any overlap. In addition, two loop primers were each incorporated in this study and the study by Hara-Kudo et al (15), while the other two studies had no loop primers (20,45).…”

“…To date, LAMP assays have been developed for Campylobacter spp. (47), Shiga toxinproducing Escherichia coli (14), norovirus (50), Staphylococcus aureus (9), Vibrio parahaemolyticus (5,26), and Vibrio vulnificus (10,12), as well as Salmonella (15,19,20,33,34,45,48). Although LAMP was reported to be rapid, specific, and sensitive, several of the Salmonella LAMP studies (33,34,48) targeted only one specific Salmonella serovar or serogroup, and none of the studies evaluated the quantification of salmonellae in produce samples by LAMP.…”