Interaction Between Shigella Flexneri And Intestinal Epithelial Cells Co-Infected With Selected Enteric Bacteria

ABSTRACT

Bacteria, intestinal epithelium, and host innate immune responses are among the most critical interacting factors that determine the fate of bacterial infections and disease outcomes. Recent studies have described multiple infections with evidence of more severe diarrhoea and molecular detection methods, suggesting the association of certain pathogens and commensal bacteria with more aggressive Shigella infection. However, the interaction between Shigella flexneri and human intestinal epithelial cells co-infected with other intestinal commensal bacteria remains unknown. Therefore, the current study investigated the interaction between S. flexneri and human intestinal epithelial cells co-infected with selected intestinal commensal bacteria. This was an experimental study and the bacteria strains tested were selected based on co-infections data obtained from previous studies. The strains were obtained from American Type Culture Collection (ATCC) and routinely grown in Luria Battani agar medium. Human colonic T84 intestinal epithelial cells, which maintain phenotypic characteristics of colonic script cells, were maintained in Dulbecco's Modified Eagle Medium-F-12 (DMEM-F12) and polarized in transwell permeable support cell culture inserts. Polarized cells were infected apically with S. flexneri 2457T and selected enteric bacteria and assessed for trans-epithelial electric resistance (TEER), invasion, cytotoxicity and cytokine induction. Furthermore, the effects on cellular morphology on non-polarized cells were assessed by scanning electron microscopy. The strains were tested in triplicates and repeated thrice. The current study showed that interaction between S. flexneri and Serratia marcescens or Citrobacter freundii influences invasion, cytotoxicity and Interleukin-8 (IL-8) production by intestinal epithelial cells in-vitro. A synergistic invasion effect appeared where the intestinal epithelial cells were co-infected with S. flexneri and S. marcescens, and S. flexneri and C. freundii but the difference was not statistically significant between the bacteria strains tested (p>0.05). However, TEER dropped significantly in monolayers infected with S. marcescens (p