Antimicrobial Activity of Bacillus Coagulans Supernatant Against Human Enteric Pathogens

Background: Chronic bacterial diarrheas are common intestinal infections that have been treated with antibiotics for many years. However, the excessive use of antibiotics has led to the development of resistance in the bacteria that cause these infections. As a result, there has been growing interest in using probiotics with antibacterial effects and a greater ability to survive stomach acidity to help control antibiotic-resistant bacteria. Objectives: In the current study, the antimicrobial activity of Bacillus coagulans (a probiotic bacterium) against four different enteric pathogens (Escherichia coli, Salmonella typhi, Shigella flexneri, and Bacillus cereus), which play a significant role in the prevalence of bacterial diarrhea, has been investigated. Methods: The antimicrobial effect of the cell-free supernatant of Bacillus coagulans against pathogens (E. coli, S. typhi, Sh. flexneri, and B. cereus) was studied using agar well-diffusion, agar disc-diffusion, as well as minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. In the MIC test, the concentrations of B. coagulans cell-free supernatant examined were 100, 50, 25, 12.5, 6.25, and 3.1 µg per mL. Each bacterial strain was tested in four replicates. Results: The antimicrobial activity of B. coagulans supernatant was not observed in either the agar well-diffusion or agar disc-diffusion results. However, MIC results showed that different concentrations of B. coagulans supernatant significantly inhibit the growth of E. coli (MIC = 25 µg/mL, P < 0.0001), S. typhi (MIC = 50 μg/mL, P < 0.0001), S. flexneri (MIC = 3.1 μg/mL, P < 0.0001), and B. cereus (MIC = 100 µg/mL, P < 0.0001). Conclusions: The MBC results showed that the minimum inhibitory concentration of the supernatant had no bactericidal effects and did not completely prevent the growth of all four pathogens. Although the MIC results indicated the antibacterial activity of B. coagulans against all four pathogens, further studies are required to draw more accurate conclusions.