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Potential in vitro competitive exclusion of Bacillus spp. strains against animal/human pathogens

Potential in vitro competitive exclusion of Bacillus spp. strains against animal/human pathogens

Name:
Thomas Wiseman

Department:
Biochemistry & Molecular Biology

Abstract:
Potential in vitro competitive exclusion of Bacillus spp. strains against animal/human pathogens Wiseman, T. W., Martin, T. A., Penaloza, A., Ma, L., Rayas Duarte, P. Oklahoma State University, Stillwater, OK Probiotics are microorganisms that possess no pathogenic characteristics or effects, and can potentially be utilized to inhibit the growth of microbial pathogenic species while also boosting metabolism of the host. The objectives of this experiment were to determine potential competitive exclusion between different strains of Bacillus spp. and pathogenic bacteria. The experiments were designed to observe how effectively a probiotic (Bacillus spp.) might inhibit the growth of a pathogenic species. Two cultivation methods were used. In the first co-cultivation method a series of ratios of a strain of Bacillus spp. (probiotic) and pathogenic Salmonella enterica serovar Muenchen (SE) were analyzed. The cultures were mixed in Tryptic Soy Broth media and incubated for 16 h. After incubation, a serial dilution was performed to 10-9 using a sample of co-cultivation. Each dilution was plated on Tryptic Soy Agar (TSA) and incubated for 16 h. This experiment was performed at least in triplicate for each strain of Bacillus spp. In addition, an overlay cultivation method was used with probiotic strains streaked on TSA plate followed by incubation for 16 h to obtain established growth. The overlay media was inoculated with SE and incubated for 16 h. Inhibition halos were measured and scored for their ability to inhibit SE. This experiment was performed at least in triplicate. The first method revealed no competitive exclusion at the density of growth and concentration ratios of probiotic and pathogen analyzed. The results might be explained in part by the slower growth of the probiotic strains. For this reason, in the second method this differential growth was addressed and will use a more active culture. The completion of the second experiment will provide additional data for consideration. Future direction of the experiment is to use E. coli as the pathogenic species, and the possibility of using an additive to aid the probiotic species.