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Aims: Salmonella is extremely diverse, with >2500 serovars that are genetically and phenotypically diverse. The aim of this study was to build a collection of Salmonella isolates that are genetically diverse and to evaluate their ability to form biofilm under different conditions relevant to a processing environment. Methods and Results: Twenty Salmonella isolates representative of 10 serovars were subtyped using Clustered regularly interspaced short palindromic repeats (CRISPR)‐typing to assess the genetic diversity between isolates of each serovar. Biofilm formation of the isolates on both plastic and stainless‐steel surfaces at 25 and 15°C was assessed. At 25°C, 8/20 isolates each produced strong and moderate biofilm on plastic surface compared to stainless‐steel (3/20 and 13/20 respectively). At 15°C, 5/20 produced strong biofilm on plastic surface and none on stainless‐steel. Several isolates produced weak biofilm on plastic (11/20) and stainless‐steel (16/20) surfaces. Serovar Schwarzengrund consistently produced strong biofilm while serovars Heidelberg and Newport produced weak biofilm. Conclusion: These results suggest that Salmonellae differ in their attachment depending on the surface and temperature conditions encountered, which may influence persistence in the processing environment. Significance and Impact of Study: These differences in biofilm formation could provide useful information for mitigation of Salmonella in processing environments. [ABSTRACT FROM AUTHOR]

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 serovars observed, especially 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 serovars detected post selective enrichment varied depending on the medium used, initial concentration, and competitive fitness factors, all which could result in minority serovars in pre-enrichment becoming dominant serovars post selective enrichment. The data presented provide a greater understanding of culture biases and lays the groundwork for investigations into robust enrichment and plating media combinations for detecting Salmonella serovars of greater concern for human health. • Different Salmonella serovars are enriched from selective enrichments in RVS and TT. • Choice of plating media influences serovars recovered from selective enrichments. • Experiments revealed starting serovar relative concentrations influence isolation. • Robust methods are vital for reliably isolating Salmonella serovars of concern. [ABSTRACT FROM AUTHOR]