Effects of Bacteriocin Extracted from Lactobacillus plantarum on Treatment-Resistant Escherichia coli Bacteria Isolated from Humans and Livestock

Background: Lactic acid bacteria (LAB) are among the most common probiotics and play a significant role in promoting health within the human intestinal microbiota. Their protective functions in the intestine include producing antimicrobial compounds, regulating the balance of the intestinal microbiome, and more. Objectives: This study aims to investigate the antimicrobial effects of bacteriocin extracted from Lactobacillus plantarum (L. plantarum) on Escherichia coli (E. coli) strains that cause treatment-resistant urinary tract infections (UTIs) in humans and mastitis in livestock. Methods: Twenty E. coli isolates were obtained from patients with UTIs and cows with mastitis. After culturing the samples on Eosin-methylene blue, McConkey agar, and blood agar, the strains were identified using biochemical tests. Bacteriocin produced by L. plantarum ATCC8014 was extracted, and its concentration was measured using the Bradford method. The antimicrobial effect of the bacteriocin was assessed using the broth microdilution method to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Additionally, the bacteriocin's antimicrobial activity was evaluated through three repetitions of disk diffusion and agar well diffusion methods. Results: The findings revealed that the MIC and MBC concentrations for all human and animal strains were 13.38 μg/mL and 26.76 μg/mL, respectively. Notably, two animal samples (No. 3 and No. 10) and one human sample (No. 6) showed lower MIC and MBC concentrations compared to the other samples and the standard E. coli sample. However, all strains were resistant to bacteriocin in the disk diffusion and agar well diffusion methods. Conclusions: The data indicate a high risk of increasing treatment-resistant E. coli strains in UTIs and livestock, which could pose a significant threat to public and animal health. Therefore, it is essential to further investigate the effects of different bacteriocins on these resistant strains, in conjunction with antibiotic therapies.