Rapid identification and absolute quantitation of zero tolerance-Salmonella enterica subsp. enterica serovar Thompson using droplet digital polymerase chain reaction

Abstract

Salmonella enterica subsp. enterica serovar Thompson (S. Thompson) poses a major threat as a pathogen to food quality and public health. The foodborne pathogen requires zero tolerance in food control. The foodborne pathogen recently caused a large-scale outbreak in Korea. Hence, there is a dire need for a sensitive and efficient assay to detect S. Thompson. This study reports for the first time the diagnostic potential of the droplet digital polymerase chain reaction (ddPCR) for absolute quantitative detection of S. Thompson. Furthermore, ddPCR performance was compared with real-time PCR (qPCR) assay. The qPCR and ddPCR assays exhibited good efficiency and linearity in the range 108 to 102 CFU/ml (R2 ≥ 0.988) and the dynamic range from 107 to 101 CFU/ml, respectively. Moreover, the ddPCR assay was more sensitive than qPCR and displayed improvement in the detection limit in pure culture and spiked egg samples by one order of magnitude to qPCR. Additionally, ddPCR enabled the rapid detection of S. Thompson at concentrations as low as 1 CFU/25 ml in pre-enrichment time for 90 min. The study can be employed as an effective tool for detecting and quantifying S. Thompson.