Mapitsi S Thantsha
University of Pretoria
South Africa
Title: In vitro antagonistic effects of Listeria adhesion protein (LAP)-expressing Lactobacillus casei against Listeria monocytogenes and Salmonella Typhimurium Copenhagen
Biography
Biography: Mapitsi S Thantsha
Abstract
Recombinant Lactobacillus casei expressing LAP reduces L. monocytogenes adhesion to, invasion into and translocation across Caco-2 cells. However, it is not known how this strain will affect pathogenicity of L. monocytogenes and other enteric pathogens in simulated intestinal fluids (SIF) under anaerobic conditions. This study investigated the effect of LAP-expressing L. casei on L. monocytogenes and S. Typhimurium in SIF under anaerobic conditions. Mammalian cells were grown to confluence, pre-treated with probiotics before exposure to pathogens suspended in SIF followed by incubation under anaerobic conditions. Adhesion and invasion of pathogens were analyzed in vitro using Caco-2 and HCT-8 cell models and their translocation was determined using trans-well model pre-seeded with Caco-2 cells. Recombinant Lb. casei inhibited adhesion of L. monocytogenes to invasion into and translocation across intestinal cells under the test conditions and reduced its cytotoxicity onto the epithelial cells. Tight junction integrity analysis using dextran fluorescein isothiocyane (DextranFITC) indicated that lower percentage of DextranFITC was recovered from basolateral chamber for Caco-2 cells pre-treated with recombinant L. casei prior to L. monocytogenes exposure. Furthermore, trans-epithelial electrical resistance (TEER) analysis revealed lower TEER reduction for cells pre-treated with recombinant probiotic. Recombinant Lb. casei protected the Caco-2 cells from damaging effects of L. monocytogenes. However, all the infection steps and intestinal cells’ structural parameters were not affected for S. Typhimurium in the presence of recombinant Lb. casei. Thus, recombinant Lb. casei shows potential specificity against L. monocytogenes without enhanced cross protection against other enteric pathogens, specifically S. Typhimuriumvar Copenhagen.