Investigation of the interaction between probiotic lactobacillus and bifidobacterium strains and pathogenic bacteria

Interest in probiotics, which have taken place in people's diets for centuries, has increased more in recent years, and the important effects of probiotics such as recovery of intestinal activities, diarrhea, lactose intolerance, allergies, strengthening of immunity and even destroying cancer cells have been emphasized. The aim of this study was to investigate the interaction between the clinical isolates of E. coli, K. pneumoniea and S. aureus and probiotic Lactobacillus acidophilus and Bifidobacterium animalis subs lactis. Five E. coli, K. pneumoniea and S. aureus strains of all species isolated in the bacteriology laboratory of Ege University Faculty of Medicine, Department of Medical Microbiology were included in the study. In order to investigate the interaction between clinical isolates and probiotic bacteria, a clinical isolate and a probiotic bacterium were cultured together in a liquid medium and then passaged to a solid medium to examine the change in colony counts after incubation. Agar diffusion method and optical density measurements were applied to investigate the effect of inhibition of supernatants of probiotic bacteria. In the agar diffusion method, after the clinical origins were planted on solid media, wells were drilled and the supernatants obtained from the cultures of probiotic bacteria were put into these wells. After incubation, inhibition around wells was evaluated according to zone diameters. In the optical density measurement method, clinical strains with 0.5McFarland turbidity were placed in microplates and probiotic supernatants were added and incubated, then optical densities were measured at the end of incubation. The data obtained were interpreted with SPSS 22.0. After the co-incubation of clinical isolates and probiotics, the number of colonies of some clinical isolates decreased but it was not found significant, in addition to that, no growth was observed in the last passages of probiotic bacteria. Different results were obtained in this method. Therefore, it was thought that the method should be modified in order to increase its reproducibility and reliability. In agar diffusion method, probiotic bacteria showed inhibitory effect on all of their clinical origins. As a result of optical density measurements, B. animalis subs. lactis was higher than L. acidophilus, probiotic bacteria showed inhibition on clinical strains ranging from 39% to 86%. It is important to further investigate the positive effects of probiotics and clarify their impact on human health. For this purpose, we believe that this study will provide a basis for further research. Reproducible and reliable methods should be developed by modifying the methods used. It is also important and necessary to carry out in vivo studies to better observe and clarify the effects of probiotics on human health.