LATE LOGARITHMIC SALMONELLA TYPHIMURIUM HEp‐2 CELL ASSOCIATION AND INVASION RESPONSE TO SHORT‐CHAIN FATTY ACID ADDITION

Abstract

The entry of Salmonella into the intestinal epithelial cells is essential for its pathogenesis. In the present stuay, late logarithmic growth (12 h) in Luria Bertani broth supplemented (25, 50, or 100 mM) with acetate, propionate, butyrate, or a mixture of the three short‐chain fatty acids (SCFA), influenced the ability ofS. typhimurium to associate and invade cultured HEp‐2 cells. The response to SCFA addition was dependent on the concentration and the pH of the medium. Cell‐association was decreased 4 to 100‐fold at pH 6 and 2 to 20‐fold at pH 7. At pH 7, invasion was increased 2‐fold when bacteria were cultured in the presence of all concentrations of acetate and 25 mM propionate or butyrate; however, a 1.5 to 163‐fold decrease in invasion occurred at pH 6 for all SCFA. The SCFA concentration also affected cell‐association and invasion of S. typhimurium, especially at pH 6. In general, for each of the SCFA at pH 6 a lower percentage of cell‐association and invasion was observed as the SCFA concentration was increased while at pH 7 decreases did not consistently occur as SCFA concentration was increased. These differences among the SCFA along with the pH effects suggest that the concentration of SCFA and the pH of the intestinal lumen may influence the expression of the invasion phenotype of S. typhimurium.

Salmonella Pathogenicity and Host Adaptation in Chicken-Associated Serovars

“…There were also indications that these S. Typhimurium responses were growth dependent, particularly in the presence of propionate and butyrate at pH 6.0, which reduced the growth rate considerably (341). However, when late-logarithmic-phase (12 h) and stationary-phase (18 h) S. Typhimurium cells were compared (342,343), all SCFAs reduced cell attachment at pH 6.0 and 7.0 but only marginally influenced invasion for late-log-phase cultures of Salmonella. The stationary-phase Salmonella cells exhibited reduced attachment only in the presence of SCFA at pH 6.0, while actual increases in invasion occurred for lower concentrations of acetate (342,343).…”

“…However, when late-logarithmic-phase (12 h) and stationary-phase (18 h) S. Typhimurium cells were compared (342,343), all SCFAs reduced cell attachment at pH 6.0 and 7.0 but only marginally influenced invasion for late-log-phase cultures of Salmonella. The stationary-phase Salmonella cells exhibited reduced attachment only in the presence of SCFA at pH 6.0, while actual increases in invasion occurred for lower concentrations of acetate (342,343). Van Immerseel et al, using avian intestinal and cecal epithelial cell lines, also observed increases in invasion of S. Enteritidis exposed to acetate for 4 h and decreases with propionate and butyrate (265,344).…”

“…Durant et al conducted a series of tissue culture studies with an epidermal carcinoma cell line (HEp-2) to determine the influence of S. Typhimurium after growth in either a mixture or separate intestinal concentrations of SCFA (acetate, propionate, and butyrate at pH 6.0 or 7.0) on its subsequent ability to adhere to and invade tissue culture cells (341)(342)(343). For S. Typhimurium incubated for 4 h in the presence of SCFA, acetate at pH 6.0 and 7.0 did not alter attachment, and only slight increases in invasion occurred, while propionate and butyrate dramatically decreased attachment and invasion at pH 6.0 but not at pH 7.0.…”

Short Chain Fatty Acids Influence Virulence Properties ofSalmonella EntericaSerovar Typhimurium

“…can combat this stress by adaptation and acid tolerance response. [12,13,25] In the present study, the surface hydrophobicity of cells during logarithmic as well as stationary phase was evaluated by binding of congo red dye to bacterial cells. Mouse lethality determination revealed a 30-fold decrease in LD 50 of SCFA exposed cells (2.163 × 10 3 organisms/mouse) as compared to the normal cells (6.46 × 10 4 organisms/mouse).…”

“…[4] One of the potential stress conditions that can be encountered by the food-borne pathogens like Salmonella is their exposure to short chain fatty acids (SCFA), particularly acetate, propionate, and butyrate. [12,13] SCFA have also been observed to modulate the expression of Salmonella pathogenicity island invasion genes including hilA and invF. These acids can be found in concentrations as high as 190 mM in gastrointestinal ecosystems harboring extensive populations of fermentative anaerobic bacteria.…”