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Research Project: Monitoring and Molecular Characterization of Antimicrobial Resistance in Foodborne Bacteria

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Title: Selective pre-enrichment method to lessen time needed to recover Salmonella from commercial poultry processing samples

item RASAMSETTI, SURENDRA - University Of Georgia
item Berrang, Mark
item Cox Jr, Nelson
item SHARIAT, NIKKI - University Of Georgia

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2021
Publication Date: 4/24/2021
Citation: Rasamsetti, S., Berrang, M.E., Cox Jr, N.A., Shariat, N. 2021. Selective pre-enrichment method to lessen time needed to recover Salmonella from commercial poultry processing samples. Food Microbiology. 99:e103818.

Interpretive Summary: Salmonella is a human bacterial pathogen that can cause illness when present on mishandled poultry meat products. Traditional culture methods employ a two-day enrichment process with a nonselective pre-enrichment followed by a selective secondary enrichment. We tested the use of a single-stage selective pre-enrichment in an effort to design a more rapid cultural recovery method. By adding selective agents usually used in secondary enrichment to a pre-enrichment medium, we were able to recover naturally occurring Salmonella from samples of broiler processing water samples. Using the new method, we were able to recover Salmonella from as many samples as with the traditional two-stage method. Furthermore, we recovered the same serotypes of Salmonella with the new method as with the traditional method. For samples that are expected to have relatively high numbers of Salmonella, the single-stage enrichment method described herein is useful and provides the industry, regulators or researchers with an accurate result while saving one day of culture time.

Technical Abstract: Conventional Salmonella detection is time consuming, often employing a 24-hour pre-enrichment step in buffered peptone water (BPW), followed by a 24-hour selective enrichment in either Rappaport Vassiliadis (RV) or tetrathionate (TT) broths before streaking onto selective indicator agar. To reduce this time, we sought to optimize pre-enrichment for Salmonella recovery by evaluating the addition of selective chemicals to BPW. Duplicate samples each representative of 500 carcasses were collected by catching processing water drip under moving carcass shackle lines immediately after feather removal in each of nine commercial processing plants. Carcass drip samples were cultured under selective pre-enrichment conditions in parallel with BPW pre-enrichment followed by RV and TT selective enrichment. Addition of bile salts (1 g/L) and novobiocin (0.015 g/L) resulted in Salmonella recovery from 89% samples when plated directly after pre-enrichment compared to 67% recovery in non-selective BPW alone. Salmonella serovar identities were determined using CRISPR-SeroSeq. Overall, serovars matched between selective pre-enrichment and traditional enrichment methods. These data suggest that increasing the selectivity of Salmonella pre-enrichment step may lessen the need for a separate selective enrichment step thereby reducing time required for Salmonella isolation by 24 hours.