Growth assessment of Salmonella enterica multi-serovar populations in poultry rinsates with commonly used enrichment and plating media

Authors: Gorski, Lisa; SHARIAT, NIKKI - University Of Georgia; RICHARDS, AMBER - University Of Georgia; SICELOFF, AMY - University Of Georgia; Aviles Noriega, Ashley; Harhay, Dayna

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2023
Publication Date: 11/28/2023
Citation: Gorski, L.A., Shariat, N., Richards, A.K., Siceloff, A.T., Aviles Noriega, A., Harhay, D.M. 2023. Growth assessment of Salmonella enterica multi-serovar populations in poultry rinsates with commonly used enrichment and plating media. Food Microbiology. 119. Article 104431. https://doi.org/10.1016/j.fm.2023.104431.
DOI: https://doi.org/10.1016/j.fm.2023.104431

Interpretive Summary: There are several hurdles in accurate, routine surveillance of foods and the environment for Salmonella contamination. Several factors, including variable fitness of Salmonella subtypes in the commonly used microbiological growth media, starting concentrations of those subtypes on the food surface, and competition between Salmonella and the natural bacteria present on foods, come together to determine which Salmonella serovars are identified from a given sample. A recently developed molecular method, CRISPR-SeroSeq allows Deep Serotype Analysis (DTA) of enrichment cultures and provides new insight into how various factors affect isolation of Salmonella serovars from contaminated foods. In this study we examined Salmonella-positive pre-enrichment cultures during routine poultry verification and assessed the recovery of Salmonella serovars in two selective enrichment growth media, Tetrathionate Broth (TT) and Rappaport Vassiliadis (RVS) broth. We observed the relative abundance of Salmonella serovars after inoculation from the same food samples depending on the growth medium used and initial concentration of the serovars in the original population. Additionally, competitive fitness factors could result in minority serovars in the original sample being observed as dominant serovars after selective enrichment. The data presented shed light on this phenomenon and lay the ground work for further investigations into robust enrichment and plating media combinations for accurate detection of Salmonella serovars that are of greater concern for human health.

Technical Abstract: Isolation of Salmonella from enrichment cultures of food or environmental samples is a complicated process. Numerous factors including fitness in various selective enrichment media, relative starting concentrations in pre-enrichment, and competition among multi-serovar populations and associated natural microflora, come together to determine which serovars are identified from a given sample. A recently developed approach for assessing the relative abundance (RA) of multi-serovar Salmonella populations (CRISPR-SeroSeq or Deep Serotyping, DST) is providing new insight into how these factors impact the serotypes observed, when different selective enrichment methods are used to identify Salmonella from a primary enrichment sample. To illustrate this, we examined Salmonella-positive poultry pre-enrichment samples through the selective enrichment process in Tetrathionate (TT) and Rappaport Vassiliadis (RVS) broths and assessed recovery of serovars with each medium. We observed the RA of serotypes detected post selective enrichment varied depending on the medium used, initial concentration, and competitive fitness factors, that could result in minority serovars in pre-enrichment being observed as dominant serovars post selective enrichment. The data presented shed light on this phenomenon and lay the groundwork for investigations into robust enrichment and plating media combinations for detecting Salmonella serovars of greater concern for human health.