title: Evaluation of real-time PCR coupled with immunomagnetic separation or centrifugation for the detection of healthy and sanitizer-injured Salmonella spp. on mung bean sprouts.
abstract: Fresh mung bean sprouts have been identified as a source of many Salmonella outbreaks worldwide. The aim of this study was to develop a rapid and accurate detection methodology for low levels of healthy and sanitizer-injured Salmonella on mung bean sprouts using real-time PCR coupled with either immunomagnetic separation (PCR-IMS) or centrifugation (PCR-cen). Initially, three parameters of IMS; specificity/sensitivity, bacterial concentration and bead incubation time were optimized. Secondly, limit of detection (LOD) was determined for the optimized PCR-IMS and PCR-cen. These two methods were compared against PCR alone (PCR) and the standard culture method (ISO) for their ability to detect Salmonella using inoculated and uninoculated sprouts. Under optimum IMS conditions (10(5)CFU/ml for 30 min), capture efficiency of Salmonella in sprout suspensions was lower than 40%, most probably due to the non-specific binding of the background microbiota. PCR-IMS and PCR-cen had a similar LOD at 10(3)CFU/ml, which was one log unit lower than PCR. Enrichment of 10h was sufficient to detect 100% of the inoculated sprouts with both PCR-IMS and PCR-cen, which was significantly faster compared to PCR and the ISO method. Moreover, the validation study using uninoculated sprouts revealed that PCR-IMS and PCR-cen were equally effective on Salmonella detection, showing 98.3% accuracy. These results suggest that PCR-cen would be the effective and less costly method for the detection of both healthy and sanitizer-injured Salmonella on mung bean sprouts.
authors: Food Science & Technology Programme, Department of Chemistry, National University of Singapore, Science Drive 4, Singapore 117543, Singapore.
authors: Qianwang
authors: Q
authors: Zheng
authors: Food Science & Technology Programme, Department of Chemistry, National University of Singapore, Science Drive 4, Singapore 117543, Singapore; Chair of Industrial and Food Microbiology, Faculty of Food Science, University of Warmia and Mazury in Olsztyn, Plac Cieszyński 1, 10-726 Olsztyn, Poland.
authors: Marta
authors: M
authors: Mikš-Krajnik
authors: Food Science & Technology Programme, Department of Chemistry, National University of Singapore, Science Drive 4, Singapore 117543, Singapore.
authors: Yishan
authors: Y
authors: Yang
authors: School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-805, Republic of Korea.
authors: Sang-Myun
authors: SM
authors: Lee
authors: Department of Food Science and Biotechnology, Kyungnam University, Changwon, Gyeongnam 631-701, Republic of Korea.
authors: Seung-Cheol
authors: SC
authors: Lee
authors: Food Science & Technology Programme, Department of Chemistry, National University of Singapore, Science Drive 4, Singapore 117543, Singapore. Electronic address: chmyukhg@nus.edu.sg.
authors: Hyun-Gyun
authors: HG
authors: Yuk
mesh_terms: D002498:Centrifugation; D005516:Food Microbiology / Q000295:instrumentation / Q000379:methods*; D018189:Immunomagnetic Separation; D060888:Real-Time Polymerase Chain Reaction; D012475:Salmonella / Q000235:genetics* / Q000302:isolation & purification*
keywords: Centrifugation; Immunomagnetic separation; Mung bean sprouts; Real-time PCR; Salmonella detection