Biofilms have the potential to form on various abiotic surfaces and have been found to be more resistant to environmental stressors. Therefore, there is a need to investigate the biofilm forming ability and characteristics of Salmonella strains isolated from poultry meat. These studies characterized the biofilm forming capabilities of 5 Salmonella strains on abiotic surfaces, and investigated changes in gene expression that are associated with Salmonella biofilm formation in 3 Salmonella strains. Salmonella biofilms were cultivated on stainless steel, concrete, rubber, and polyethylene under static and shear stress conditions. Biofilm matrix density was determined using a modified crystal violet assay, and attached cells were enumerated by direct plating on tryptic soy agar plates. Additionally, biofilm development was verified using scanning electron microscopy. Extracellular matrix density was affected by a surface-incubation condition interaction, in which the OD600 was higher on stainless steel under shear stress, as compared to static incubation (P < 0.001). On polyethylene, the OD600 was higher under static incubation (P < 0.001). The number of attached cells was highest on polyethylene under shear stress, irrespective of strain (6.4 log/coupon; P < 0.001). The study tracked changes in the expression of the biofilm-associated genes csgD, bapA, bcsA, adrA, and luxS. The gene expression levels in 24 h planktonic cells, 4-day old biofilms, and 5-day old biofilms were compared to those in 12 h planktonic cells and normalized to 16S RNA. Three different Salmonella serovars were used in this study: Salmonella Typhimurium, Reading, and Kentucky. Upregulation of csgD, bcsA, adrA, and luxS at 24 h was observed exclusively in Salmonella Reading (P = 0.028). In 4-day old biofilms, downregulation of all 5 genes was detected (P < 0.001). However, in 5-day old biofilms, the expression of bapA, bcsA, adrA, and luxS increased across all tested Salmonella serovars. These findings highlight the variations in gene expression across different Salmonella serovars, emphasizing the need to remove and prevent Salmonella attachment on food contact surfaces. Through further investigation, it may be possible to establish environmental stress thresholds for biofilm formation and optimize intervention strategies to mitigate Salmonella attachment and persistence on industrial materials.
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-7196 |
| Date | 10 May 2024 |
| Creators | Thames, Hudson |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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