Bio-controlling capability of probiotic strain Lactobacillus rhamnosus against some common foodborne pathogens in yoghurt

Despite there being many food preservation techniques, foodborne illnesses are still a growing problem. Developing alternative natural methods to control foodborne pathogens is still necessary. The antimicrobial activity of Lactobacillus rhamnosus was studied against four common foodborne pathogens, both in vitro and in a food model (yoghurt). Using an agar well diffusion assay, acidified L. rhamnosus cell free supernatant was shown to significantly inhibit all pathogens tested: Escherichia coli O157:H7, Staphylococcus aureus, Yersinia enterocolitica and Salmonella enterica serovar Typhimurium. Moreover, neutralised supernatant also had an antimicrobial effect against most pathogens, which proved the presence of inhibitory compounds rather than acids. With addition of L. rhamnosus to pathogen-spiked yoghurt, complete elimination or at least reductions of pathogen counts was achieved. Pathogen reduction by L. rhamnosus was correlated with the initial count. From this pilot study, addition of L. rhamnosus to yoghurt seems to be a beneficial and applicable bio-control strategy.