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Interaction and effects of probiotic Bacillus on pathogenic Salmonella enteritidis (SE)

Interaction and effects of probiotic Bacillus on pathogenic Salmonella enteritidis (SE)

Brienna Milleson

Biochemistry & Molecular Biology

Probiotics are microorganisms that thrive in the gastrointestinal tract (GIT) of both animals and human hosts. They preserve the good microbiota in the GIT by preventing the adhesion of pathogenic microorganisms, promoting the overall health of the host. They are commonly used in agriculture as a means to promote the growth and fitness of livestock, often lowering the need for antibiotic use. The objective of this study was to evaluate the effect of isolated probiotic strains on the growth of the pathogenic bacteria Salmonella enterica serovar Muenchen (SE). This bacterium is an important target for effective probiotics, as it is a common reservoir of pathogenic antimicrobial and antidrug resistance commonly seen and spread in animals in the food industry, particularly in poultry. Ten probiotic strains were isolated and identified as Bacillus ssp. These strains present some probiotic characteristics as survival in the chicken GIT. For this reason, we are interested in evaluating the competitive exclusion of this strains with the SE strain. The competitive exclusion of the strains versus SE was observed using the overlay technique. This entails Luria-Bertani (LB) plates, inoculated with probiotic strains, incubated at 39°C for 16 h. These probiotic-inoculated plates were overlaid with 10 mL of LB soft agar containing a 109 CFU/mL of SE. After further incubation, the plates were assessed for zones of inhibition on SE, seen as clear halos in the medium, which were measured gauge the ability of the probiotic strains to inhibit SE infection. The results obtained so far showed several of the strains having antagonistic effects on SE, which is promising for evaluation of their probiotic strength. With these encouraging preliminary results, the next step is to confirm their effectiveness by performing in vivo assay challenge studies in broiler chickens.