Synergistic antibacterial effects of postbiotics from Pediococcus acidilactici and Aspergillus fumigatus against Escherichia coli (ATCC ۲۵۹۲۲)

Background: The increasing resistance of pathogenic bacteria to conventional antibiotics has necessitated the search for alternative antimicrobial agents. A postbiotic is any molecule or product resulting from the metabolic activity of living organisms that produces health-giving effects in the host. This study investigated the antimicrobial activity of postbiotic metabolites produced by Pediococcus acidilactici and Aspergillus fumigatus extracted from large animal feed against Escherichia coli (ATCC ۲۵۹۲۲). Methods: This study utilised Escherichia coli (ATCC ۲۵۹۲۲) as the target pathogen. The Escherichia coli and Pediococcus acidilactici strains were obtained from the Iranian Biological Resource Center (IBRC) in Tehran, Iran. Samples of large animal feed were collected. Aspergillus fumigatus were isolated, and Pediococcus acidilactici metabolites were prepared in liquid culture using Sabro dextrose broth and Mueller-Hinton agar (MHA), respectively, in a shaker incubator. After incubation, the culture was centrifuged at ۱۰,۰۰۰ × g for ۱۵ minutes to separate the cells from the supernatant. The supernatant, containing the postbiotic metabolites, was filtered through a ۰.۲۲ μm membrane filter to ensure sterility. The postbiotic mixture was prepared by combining equal volumes of metabolites from Aspergillus fumigatus and Pediococcus acidilactici. The broth micro dilution method was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the postbiotics mixture. Additionally, the disk diffusion and well diffusion methods were employed to evaluate the antimicrobial activity.