NaCl Effect on Invasive Staphylococcus aureus Invasion and Immune Responses in the Intestinal Epithelial Cell

Abstract

This study investigated the immune responses, which may cause chronic problems through intestinal invasion by Staphylococcus aureus, which is wellknown to cause intoxication rather than invasion, and NaCl effect on the invasion. Five S. aureus strains were cultured and exposed to NaCl concentrations of 0%, 2%, 4%, or 6% supplemented in tryptic soy broth. The surviving cells were isolated by subsequent exposure of the culture on tryptic soy agar containing 0%, 2%, 4%, or 6% NaCl. The resulting cells were subjected to assays evaluating the invasion efficiency into Caco-2 cells, the level of immune responses generated, and the resultant cell viability. For S. aureus strains that invaded Caco-2 cells, the transcriptional analysis for adhesion related genes was conducted by quantitative real-time PCR. Only S. aureus ATCC14458 demonstrated obvious invasion into Caco-2 cells. Invasion efficiency of the strain was influenced by NaCl levels, and expression levels of the cell adhesion related genes were higher at 2%, 4%, and 6% NaCl. In addition, inflammation-related factors were increased. These results indicate that S. aureus ATCC14458 can invade Caco- 2 cells, which may cause infectious illness and other chronic symptoms, and that NaCl increases the extent of Caco-2 cell invasion by expressing specific genes.