Comparison of selective enrichment and plating media for Salmonella isolation from broiler carcasses

Authors: OBE, TOMI - University Of Georgia; Berrang, Mark; Cox Jr, Nelson; House, Sandra; SHARIAT, NIKKI - University Of Georgia

Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2021
Publication Date: 9/3/2021
Citation: Obe, T., Berrang, M.E., Cox Jr, N.A., House, S.L., Shariat, N. 2021. Comparison of selective enrichment and plating media for Salmonella isolation from broiler carcasses. Journal of Food Safety. 41(6):e12928. https://doi.org/10.1111/jfs.12928.
DOI: https://doi.org/10.1111/jfs.12928

Interpretive Summary: Salmonella, a dangerous human pathogen, is commonly associated with poultry. In order to assure production of safe and wholesome poultry meat products, it is critical that the best methods are used to detect Salmonella for regulatory oversight and commercial self testing We compared various combinations of some of the most common enrichment broths and plating media for detection of Salmonella from broiler carcasses. Broiler carcasses were rinsed in buffered peptone water which was used to inoculate three different enrichment broth protocols: Rappaport Vassiliadis broth (RV) 24 h incubation, TT -Hajna broth (TT) 24 h incubation and TT incubated for 24 h then transfered to RV broth for an additional 24 h incubation (RV-TT). Following completion of the enrichment incubation(s), each broth was used to inoculate three different plating media: Hektoen (HE), Brilliant Green Sulfa (BGS), and Xylose-Lysine-Tergitol-4 (XLT4). All plating media were incubated and colonies characteristic of Salmonella were removed, confirmed using biochemical and serological tests and serotyped. Salmonella was detected by at least one method from all carcasses. Overall, HE agar did not allow detection of Salmonella as often as the other two plating media regardless of enrichment broth. There were some instances when different protocols allowed detection of different serotypes of Salmonella. However, the combination of RV and TT enrichment followed by BGS and XLT4 plating allowed recovery of all serotypes detected. These data show that method choice can influence Salmonella recovery and suggest that concurrent use of more than one method may be the best approach.

Technical Abstract: Salmonella detection and isolation rely on different selective enrichment media, which can influence which serovars are detected. The objective of this study was to compare Salmonella recovery from broiler carcass rinses using three different selective enrichment protocols and three differential plating agars. Eight pre-chill broiler carcasses were collected at a commercial slaughter facility. Each carcass was subjected to whole carcass rinse procedure in buffered peptone water (BPW). An aliquot of the rinse and whole carcasses in the remaining rinse were incubated as a pre-enrichment before subculturing in selective enrichment broths (Rappaport Vassiliadis [RV], Tetrathionate Hajna [TT], and TT to RV in series [TT-to-RV]). Enriched samples were streaked on the three differential agars (Hektoen Enteric [HE], Brilliant Green Sulfa [BGS], and Xylose-Lysine-Tergitol-4 [XLT-4]). Salmonella was isolated from all eight carcasses. Considering all sample preparations as independent subsamples, Salmonella was detected in 88% (128/144) of subsamples with a 100% recovery from the TT-to-RV enrichment, and 92% and 71% from RV and TT broths, individually. A high concordance in recovery on BGS vs. XLT-4 agar plates was observed compared to HE vs. BGS and HE vs. XLT-4 plates. These data suggest that choice of pre-enrichment method, selective enrichment medium, and differential agar can influence the recovery of Salmonella from poultry samples.