Short Chain Fatty Acids Influence Virulence Properties ofSalmonella EntericaSerovar Typhimurium

Abstract

The present study investigated SCFA exposed Salmonella enterica serovar Typhimurium for its virulence characteristics such as mouse lethality adhesion, surface hydrophobicity, phagocytic uptake, intracellular survival within the murine peritoneal macrophages, induction of acid tolerance response (ATR), and the expression of outer membrane proteins (OMPs). Lethal dose (LD50) for mice was found to be more for SCFA exposed cells as compared to the normal cells. In vitro adherence to murine intestinal epithelial cells as well as surface hydrophobicity of SCFA exposed cells were found to be lower than the normal cells. Though the phagocytic uptake of normal cells and SCFA exposed cells was similar, the SCFA exposed cells exhibited increased intracellular survival as compared to the normal cells, which were completely killed after 4 h. Moreover, SCFA exposed cells also survived exposure to extremely low pH (3.0). Outer membrane proteins extracted from SCFA exposed cells revealed an enhanced expression of proteins (porins) at 4% SCFA concentration. Thus, SCFA exposure may contribute to enhanced virulence of Salmonella enterica serovar Typhimurium by increased intracellular survival, induction of acid tolerance response, and the enhanced expression of outer membrane matrix proteins (porins).

The Acid Tolerance Response of Salmonella spp.: An adaptive strategy to survive in stressful environments prevailing in foods and the host

“…It was also shown that stationary-phase cultures of S. Typhimurium exposed for short time periods to moderate acid conditions also developed an ATR (Bang et al, 2000;Bang et al, 2002;Koutsoumanis & Sofos, 2004;Lee et al, 1994;Lin et al, 1995). While in all of these studies the acid adaptation and the lethal acid treatments were carried out in laboratory media acidified with hydrochloric acid, some evidence has more recently emerged demonstrating that S. Typhimurium can also mount an ATR when organic acids are used, either for adaptation through short-time exposures or for acid challenge (Baik et al, 1996;Greenacre et al, 2003;Kwon & Ricke, 1998;Rishi et al, 2005).…”

“…Enteric bacteria are protected from killing under extremely acidic conditions of pH 2.5 when they are inoculated onto certain solid food sources Gawande and Bhagwat (2002) Growth at pH 5.5 pH 3.0 onto polyethersulfone membranes or in planktonic state Acid adaptation increases S. Typhimurium acid resistance onto solid surfaces Rishi et al (2005) Short-time exposure to different short chain fatty acids at pH 7.0 pH 3.0 Exposure to short chain fatty acids contributes to enhance virulence of S. Typhimurium Yuk and Schneider (2006) Growth in the presence of glucose Long-term exposition (24 h When stationary-phase S. Typhimurium cells are used, the influence of the adaptation pH value seems to be different. Thus, Lee et al (1994), growing a series of overnight cultures so that their final pH values ranged from 7.4 to 4.3, showed that stationary-phase cells taken from cultures with a final pH b 5.0 survived significantly better than those obtained at higher pH values.…”

Protective effect of probiotics on Salmonella infectivity assessed with combined in vitro gut fermentation-cellular models

“…S . Typhimurium), by inducing an acid tolerance response or increasing expression of porins [27]. To our knowledge, the effects of an infected gut microbiota, including its metabolites and probiotic treatment on intestinal cells has not been previously reported.…”

The metabolic pathways utilized by Salmonella Typhimurium during infection of host cells

“…Acidification of the SCV has been shown to be an inducer of SPI2 expression within macrophages, and lactate and acetate have been found to repress and induce SPI1 expression, respectively (Durant et al ., ; Lawhon et al ., ; van Immerseel et al ., ; Rishi et al ., ). The finding that acetate and lactate are produced by intracellular S .…”