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P3-05 Evaluation of Lateral Flow Devices for Detection of Escherichia coli O157:H7 in Raw Milk and Produce

Wednesday, July 31, 2013
Exhibit Hall (Charlotte Convention Center)
Willis Fedio, New Mexico State University, Las Cruces, NM
Ruben Zapata, New Mexico State University, Las Cruces, NM
Paul Browning, New Mexico State University, Las Cruces, NM
Ken Yoshitomi, U.S. Food and Drug Administration, Bothell, WA
Karen Jinneman, U.S. Food and Drug Administration, Bothell, WA
Lyssa White, New Mexico State University, Las Cruces, NM
Ruiqing Pamboukian, U.S. Food and Drug Administration, Rockville, MD
Steve Weagant, Weagant Consulting, Poulsbo, WA
Introduction: Detection of Escherichia coli O157:H7 in produce and raw milk by standard cultural methods can be difficult due to the high background microflora. Assays such as lateral flow devices can offer rapid screening of enriched samples and are cost effective.

Purpose: This study evaluated the reliability of using lateral flow devices for E. coli O157:H7 detection using FDA BAM methods or modified BAM procedures.

Methods: Romaine lettuce, cilantro, raw milk, spinach and strawberries were inoculated at a low level (for fractional recovery) and a higher inoculum level. Twenty replicates at each inoculum level were tested per food matrix, as well as eight uninoculated controls.  Rinsates (125 ml) prepared from inoculated Romaine lettuce, cilantro, and spinach were added to 125 ml 2XmBPWp for enrichment. For strawberry samples, 1 pound samples were enriched in 1 l of broth.  Raw milk was enriched (25 g) in 225 ml of mBPWp.  Each food was enriched for 5 hours at 37°C then acriflavin, cefsulodin and vancomycin (ACV) were added, and the enrichments were incubated for an additional 15 h at 42°C.The enrichments were all screened with RapidChek E. coli O157, Neogen Reveal 1.0 for E. coli O157:H7, Neogen Reveal 2.0 for E. coli O157:H7 and VIP Gold EHEC lateral flow devices, qPCR and cultural detection on selective media.

Results: Lateral flow devices were as efficient as cultural recovery for identifying EHEC in produce rinses and strawberries. However at the low level (0.1 CFU/g), the Neogen 2.0 test device was significantly less effective than cultural recovery for raw milk.

Significance: E. coli O157:H7 lateral flow devices accelerated detection of E. coli O157:H7 from leafy greens using a rinsate procedure, strawberries with a soak procedure and raw milk with direct enrichment of 25 g samples. However, the Neogen 2.0 device showed reduced sensitivity detecting E. coli O157:H7 at low contamination levels in raw milk.

Back to: Poster Session 3 - Applied Laboratory Methods, Novel Laboratory Methods, Produce, Risk Assessment
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