University of Pretoria
Title: In vitro antagonistic effects of Listeria adhesion protein (LAP)-expressing Lactobacillus casei against Listeria monocytogenes and Salmonella Typhimurium Copenhagen
Mapitsi S Thantsha has completed her PhD from University of Pretoria, South Africa. She is a Senior Lecturer in the Department of Department of Microbiology and Plant Pathology, University of Pretoria. She is an alumnus of the Fulbright Scholarship Program, having spent time as a Visiting Scholar in the Department of Food Science, Purdue University, USA. She has published 14 papers in reputed journals, 2 book chapters and has presented at national and international conferences. She has been involved in human capacity development in terms of both undergraduate and postgraduate students’ training.
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.