title: Evaluation and comparison of rapid methods for the detection of Salmonella in naturally contaminated pine nuts using different pre enrichment media.
abstract: Foodborne outbreaks, involving pine nuts and peanut butter, illustrate the need to rapidly detect Salmonella in low moisture foods. However, the current Bacteriological Analytical Manual (BAM) culture method for Salmonella, using lactose broth (LB) as a pre enrichment medium, has not reliably supported real-time quantitative PCR (qPCR) assays for certain foods. We evaluated two qPCR assays in LB and four other pre enrichment media: buffered peptone water (BPW), modified BPW (mBPW), Universal Pre enrichment broth (UPB), and BAX(®) MP media to detect Salmonella in naturally-contaminated pine nuts (2011 outbreak). A four-way comparison among culture method, Pathatrix(®) Auto, VIDAS(®) Easy SLM, and qPCR was conducted. Automated DNA extraction techniques were compared with manual extraction methods (boiling or InstaGene™). There were no significant differences (P > 0.05) among the five pre enrichment media for pine nuts using the culture method. While both qPCR assays produced significantly (P ≤ 0.05) higher false negatives in 24 h pre enriched LB than in the other four media, they were as sensitive as the culture method in BPW, mBPW, UPB, and BAX media. The VIDAS Easy and qPCR were equivalent; Pathatrix was the least effective method. The Automatic PrepSEQ™ DNA extraction, using 1000 μL of pre enrichment, was as effective as manual extraction methods.
authors.affiliation: FDA-Center for Food Safety and Applied Nutrition, 5100 Paint Branch Parkway, College Park, MD 20740, USA. Electronic address: hua.wang@fda.hhs.gov.
authors.forename: Hua
authors.initials: H
authors.lastname: Wang
authors.affiliation: FDA-Center for Food Safety and Applied Nutrition, 5100 Paint Branch Parkway, College Park, MD 20740, USA.
authors.forename: Vikas S
authors.initials: VS
authors.lastname: Gill
authors.affiliation: FDA-Pacific Regional Laboratory-Southwest, 19701 Fairchild, Irvine, CA 92612, USA.
authors.forename: Chorng-Ming
authors.initials: CM
authors.lastname: Cheng
authors.affiliation: FDA-Center for Food Safety and Applied Nutrition, 5100 Paint Branch Parkway, College Park, MD 20740, USA.
authors.forename: Narjol
authors.initials: N
authors.lastname: Gonzalez-Escalona
authors.affiliation: FDA-Coordinated Outbreak Response and Evaluation Network, 5100 Paint Branch Parkway, College Park, MD 20740, USA.
authors.forename: Kari A
authors.initials: KA
authors.lastname: Irvin
authors.affiliation: FDA-Center for Food Safety and Applied Nutrition, 5100 Paint Branch Parkway, College Park, MD 20740, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Zheng
authors.affiliation: FDA-Center for Food Safety and Applied Nutrition, 5100 Paint Branch Parkway, College Park, MD 20740, USA.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Bell
authors.affiliation: FDA-Center for Food Safety and Applied Nutrition, 5100 Paint Branch Parkway, College Park, MD 20740, USA.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Jacobson
authors.affiliation: FDA-Center for Food Safety and Applied Nutrition, 5100 Paint Branch Parkway, College Park, MD 20740, USA.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Hammack
mesh_terms: D015169:Colony Count, Microbial / Q000295:instrumentation / Q000379:methods*; D003470:Culture Media / Q000737:chemistry / Q000378:metabolism; D005506:Food Contamination / Q000032:analysis; D009754:Nuts / Q000382:microbiology*; D028223:Pinus / Q000382:microbiology; D012475:Salmonella / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification
chemical_list: D003470:Culture Media
keywords: DNA extraction; Pathatrix(®) Auto; Pine nuts; Pre enrichment media; PrepSEQ™; Salmonella; VIDAS(®) Easy; qPCR