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P3-17 Early Recovery of Salmonella enterica from Cilantro Using Nonselective Preenrichment Broths

Tuesday, July 28, 2015
Hall B (Oregon Convention Center)
Ninalynn Daquigan , U.S. Food and Drug Administration , Laurel , MD
Christopher Grim , U.S. Food and Drug Administration , Laurel , MD
Laura Ewing , U.S. Food and Drug Administration , Laurel , MD
Nicole Addy , Oak Ridge Institute for Science and Technology , Oak Ridge , TN
Junia Jean-Gilles Beaubrun , U.S. Food and Drug Administration , Laurel , MD
Darcy Hanes , U.S. Food and Drug Administration , Laurel , MD
Karen Jarvis , U.S. Food and Drug Administration , Laurel , MD
Introduction: Salmonella enterica is a leading cause of foodborne illness in the United States. Current enrichment methods for Salmonella from produce require initial 24 hour incubation in a nonselective broth and additional 24 hour incubation in two selective media, Rappaport-Vassiliadis (RV) medium and Tetrathionate (TT) broth. Decreasing this time to detection would greatly impact traceback analysis efforts during outbreaks and routine surveillance.

Purpose: This study evaluates the recovery of two S. enterica serovars, Newport and Tennessee, after a reduced initial incubation period in nonselective broth with the goal of decreasing the total time of culture enrichment from 48 to 24 hours prior to selective plating.

Methods: Seven cilantro samples (50 g) were inoculated with S. enterica Newport or Tennessee (< 10 CFU/50 g) and processed according to the FDA Bacteriological Analytical Manual (BAM) with modifications. Five nonselective enrichment broths (modified buffered peptone water (mBPW), universal preenrichment broth (UP), lactose broth (LB), Davis minimal broth (DMB), and trypticase soy broth (TSB)) were evaluated. Five aliquots of each broth were inoculated into TT and RV after a static 37°C incubation ranging from three to seven hours, incubated at 42.5°C overnight, and streaked onto Xylose-Lysine-Tergitol 4 selective agar.

Results: Five-hour static initial nonselective enrichment was the earliest timepoint in which both serovars were recovered from TT samples. Detection of Salmonella from earlier timepoints was variable with no consistent association between nonselective preenrichment broth, selective broth, and Salmonella detection.

Significance: The enrichment of Salmonella from cilantro was reduced from 48 to 24 hours with a five-hour static incubation in nonselective preenrichment broth prior to inoculation into selective broths, significantly decreasing the time to detection.

Back to: Poster Session 3 – Laboratory and Detection Methods, Sanitation; Antimicrobials; Produce; Epidemiology
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