Comparative characterization of Listeria monocytogenes strains sensitive and resistant to the action of bacteriocins

IBARGUREN C

CABA

Workshop; Humboldt Colloquium Shaping the Future of German-Argentinian Scientific Cooperation - The Role of Curiosity-Driven Research; 2018

Fundación Alexander von Humboldt

My current research work continues with the line developed since my PhD thesis. Different Enterococcus lactic bacteria, selected for their ability to synthesize bacteriocins with a clear anti-Listeria monocytogenes effect, were isolated in the group. The antimicrobial potential of these bacteriocins encouraged the analysis of alternatives for their optimal application in food. Thus, the immobilization of bacteriocins on different food grade supports (silicates, pectin microcapsules and biopolymer edible films) was studied. Furthermore, during my stay in Germany, funded by an Alexander von Humboldt Georg Forster Research Fellowship for Posdoctoral Researchers, I had the opportunity to study and positively characterize the interaction between the commercial bacteriocin nisin and natural montmorillonite as a potential vehicle for this bacteriocin in food. Also, based on hurdle technology, the possible synergic effect between bacteriocins and different food additives used for the control of L. monocytogenes was compared. As well, the synergic antimicrobial action between the bacteriocins and flavonoid esters supported on gelatin films against L. monocytogenes and other food pathogens (Bacillus cereus and Staphylococcus aureus) was also studied. Regarding the food application of these bacteriocines, we obtained very promising results when applying the antimicrobials included in agar films as coatings in cheeses contaminated in situ with L. monocytogenes. Currently, we are working on the design of alternative food-grade culture media for the sustainable production of bacteriocins, as well as the evaluation of alternatives for the inclusion of these antimicrobials in cheeses, or other products of regional interest. Finally, we also acquired expertise in the management of L. monocytogenes. Thus, several microbiological analyses were done for their detection and isolation from food samples. On the other hand, we detected the generation of resistance in strains of L. monocytogenes exposed to the action of some bacteriocins studied in the group. These resistant strains were isolated and we advanced on the comparative characterization of phenotypic and physiological properties among L. monocytogenes sensitive and resistant strains. Also, we have been working in the comparative evaluation of the resistant/sensitive strains capacity of biofilms formation and growth in presence of different food preservation stress conditions. In order to understand this bacteriocin-resistance generation in L. monocytogenes strains, it is planned to perform comparative proteomic analyses of changes in the protein expression between L. monocytogenes sensitive and resistant. In addition, a comparative analysis of the transcriptomic response of virulence genes of susceptible and resistant L. monocytogenes cells is scheduled.