Antibiotic Susceptibility Profiling of Over-the-Counter Probiotic Supplements

Leandra Hess The University of Findlay, Kathryn Kelly The University of Findlay, Hannah McColl The University of Findlay, Hannah Cope The University of Findlay
Faculty Sponsor(s): Robert Charvat The University of Findlay
Intestinal microflora are pivotal in aiding with digestion, stimulating the immune system, and providing protection from enteric pathogens. They are often caught in the crossfire during antibiotic treatments intended to eliminate invading infectious agents. Antibiotic therapy results in a reduction in the population of beneficial bacteria as well as an increased risk for more severe infections, including Clostridium difficile. Additionally, antibiotic-associated diarrhea, is a consequence of such treatments. To alleviate this symptom, individuals are turning to probiotic supplements, which consist of non-pathogenic bacteria that induce health benefits, such as digestive regularity, prevention of disease, and replenishment of the natural microbiota. However, if the bacteria present in the probiotic supplements are sensitive to antibiotics, they would fail to reestablish the intestinal microflora. The purpose of this project was to test the hypothesis that bacterial strains contained within probiotics are resistant to common antibiotics. The antibiotic susceptibility was assessed for several over-the-counter probiotic supplements via the Kirby-Bauer Disk Diffusion method on medium specific for lactobacilli propagation. After measuring the zones of inhibition, the probiotics were surprisingly sensitive to two-thirds of the antibiotics tested, with the observed growth inhibition greatly exceeding predetermined standards for susceptibility. These results suggest that concomitantly taking probiotic supplements during a course of antibiotics is likely futile for replenishing the intestinal microbiota. We intend to expand the study to include additional antibiotics and supplements of varying formulations to gain insight into which strains may possess the greatest resistance and be the most effective for recolonization of the gastrointestinal tract.
Oral Presentation

When & Where

09:15 AM
Gallahue Hall 106