title: Evaluation of commercial kit based on loop-mediated isothermal amplification for rapid detection of low levels of uninjured and injured Salmonella on duck meat, bean sprouts, and fishballs in Singapore.
abstract: The objective of this study was to evaluate performance of the commercial kit based on loop-mediated isothermal amplification (LAMP) in comparison with the International Organization for Standardization method for detecting uninjured and sublethally injured Salmonella cells artificially inoculated at levels of 10(0) and 10(1) CFU/25 g on raw duck wing, raw mung bean sprouts, and processed fishballs. Injured cells were prepared by a heat treatment for duck wings and fishball samples and a chlorine treatment for bean sprout samples. Additionally, a validation study was performed on naturally contaminated food samples sold in Singapore. A total of 110 samples of each commodity were analyzed in this study. Regardless of inoculum levels, the detection by the commercial LAMP kit showed 100% sensitivity and specificity for both inoculated and uninoculated samples compared with the International Organization for Standardization method, with the exception of bean sprout samples. Only 20% of bean sprout samples inoculated with 10(0) CFU/25 g injured Salmonella cells were positive by using the commercial LAMP-based kit. However, all negative samples became positive following a secondary enrichment in Rappaport-Vassiliadis medium with soy broth or after concentration by centrifugation. These results suggest that secondary enrichment or centrifugation should be considered as an additional step to increase the sensitivity of the commercial LAMP-based kit with low numbers of injured target cells in samples with high background microflora (such as mung bean sprouts). The validation study also showed that the commercial LAMP-based kit provided 91% sensitivity and 95% specificity for naturally contaminated samples. Thus, this study demonstrates that the commercial LAMP-based kit might be a cost-effective method, as this system could provide rapid, accurate detection of both uninjured and injured Salmonella cells on raw duck wings, raw mung bean sprouts, and processed fishballs in less than 26 h.
authors.affiliation: Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543.
authors.forename: Hazel Sin Yue
authors.initials: HS
authors.lastname: Lim
authors.affiliation: Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543.
authors.forename: Qianwang
authors.initials: Q
authors.lastname: Zheng
authors.affiliation: Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543; Industrial and Food Microbiology, Faculty of Food Science, University of Warmia and Mazury in Olsztyn, Plac Cieszyński 1, 10-726 Olsztyn, Poland.
authors.forename: Marta
authors.initials: M
authors.lastname: Miks-Krajnik
authors.affiliation: 3M Asia Pacific Pte Ltd., 1 Yishun Avenue 7, Singapore 768923.
authors.forename: Matthew
authors.initials: M
authors.lastname: Turner
authors.affiliation: Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543. chmyukhg@nus.edu.sg.
authors.forename: Hyun-Gyun
authors.initials: HG
authors.lastname: Yuk
mesh_terms: D000818:Animals; D015169:Colony Count, Microbial; D003362:Cost-Benefit Analysis; D004269:DNA, Bacterial / Q000302:isolation & purification; D004372:Ducks; D007887:Fabaceae / Q000382:microbiology*; D005396:Fish Products / Q000382:microbiology*; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology / Q000379:methods*; D006358:Hot Temperature; D008460:Meat / Q000382:microbiology*; D021141:Nucleic Acid Amplification Techniques / Q000379:methods; D019779:Salmonella enterica; D012846:Singapore
chemical_list: D004269:DNA, Bacterial