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

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Title: Use of selective pre-enrichment broth reduces the time required for Salmonella recovery

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

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/12/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Conventional Salmonella surveillance requires a week for isolation, confirmation, and subsequent serotyping. This time burden can be detrimental within the context of an outbreak. Salmonella isolation involves multiple steps: a 24-hour non-selective pre-enrichment step in buffered peptone water (BPW) is followed by a 24-hour selective enrichment in either Rappaport Vassiliadis (RV) or tetrathionate (TT) broths, and these are streaked onto selective indicator agar. This is followed by further biochemical tests and serotyping to confirm the presence of Salmonella and to identify the serovar. To reduce the time by 24 hours, we investigated whether it was possible to combine the pre-enrichment and enrichment steps by addition of some selective chemicals to BPW after four hours of a pre-enrichment step and recover Salmonella by plating directly from this culture. Duplicate samples, each representative of 500 broiler 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 three different 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% (16/18) samples when plated directly after pre-enrichment compared to 67% (12/18) recovery in non-selective BPW alone. The serovar profiles were determined using CRISPR-SeroSeq and showed concordance between selective pre-enrichment and traditional enrichment cultures. These results suggest that increasing the selectivity of BPW facilitates direct plating of Salmonella, thus reducing the conventional protocol by a day without the need for a separate selective enrichment step.