Synergistic Modulation of Gut Microbiota by Bioactive Peptides and Probiotics: A Novel Approach Towards Better Health Outcomes

Background: Probiotics have been found to be beneficial for human beings through the modulation of intestinal bacteria and inhibition of pathogens. In light of the increased prevalence of multidrug resistant uropathogens, there is a need for alternative therapies than antibiotics. Objectives: This study assessed the capacity of three probiotics (Lactobacillus acidophilus, Lactic Acid Bacillus and Probiotic Consortium) to inhibit three important uropathogens; Escherichia coli, Klebsiella and Staphylococcus aureus with a view of understanding their antibacterial mechanism of action. Methods: In vitro co-cultures were set up to monitor the growth of the pathogens, the development of biofilms and acidification of the culture media for 24 hours. Biofilm biomass inhibition was assessed using crystal violet microtiter plate assays. The molecular responses to probiotics of Escherichia coli was also assessed by analysis of transcriptomics of cell envelope stress genes (omp) and molecular chaperones (dnaK, chap). Results: The efficacy of biofilm inhibition was highly strain-dependent, such that Lactobacillus acidophilus always showed significantly greater broad spectrum biofilm inhibition than both the probiotic consortium and Lactic Acid Bacillus. Escherichia coli Biofilm Inhibition: L. acidophilus gave the highest inhibition of 66.67%, whereas the probiotic consortium inhibited 59.05% of the biofilms and Lactic Acid Bacillus 3.81%. Klebsiella Biofilm Inhibition: The best biofilm inhibition was observed with L. acidophilus with 78.00% compared to the probiotic consortium (61.11%) and Lactic Acid Bacillus (42.50%). Staphylococcus aureus Biofilm Inhibition: L. acidophilus showed maximal biofilm inhibition of 69.09% compared to 54.55% inhibition from the probiotic consortium. Inhibition showed high correlation with medium acidification and antimicrobial metabolite production. Transcriptome analysis: treatment with L. acidophilus caused severe cell envelope stress in E. coli (5.4-fold increase in expression of omp) and impaired intracellular stress response in E. coli with the inhibition of molecular chaperone (dnaK -4.0-fold and chap -2.6-fold. Conclusion: Lactobacillus acidophilus is a strong broad spectrum antibiofilm agent that targets Gram-negative and Gram-positive uropathogens. Antimicrobial activity of this bacterium is exerted through acidification, metabolite production, cell envelope stress induction, and regulation of stress response mechanisms.