Study of the Effect of Bacteriocin-producing Bacillus subtilis Strains on Beta-lactamase-producing Pathogenic Bacteria

Background: The emergence of antimicrobial resistance results in morbidities and mortalities associated with many bacterial infections and is a major concerning issue in front of the healthcare system. As a part of a competitive adaptive strategy for its growth, gram-positive bacteria like Bacillus subtilis produce antimicrobial peptides; bacteriocins. These peptides protect other bacterial species. Objectives: To counter antimicrobial resistance, bacteriocins can be considered a potential drug option against drug-resistant microorganisms. Methods: After isolation and characterisation of B. subtilis from the 5 collected soil samples, the bacteriocin was extracted from these bacteria by using the ‘solvent extraction method’, characterised, and then purified to evaluate its antimicrobial activity against pathogenic bacteria like; Streptococcus pyogenes, Salmonella typhi, Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii by using ‘Kirby-Bauer disc diffusion’, method. The bacteriocin stability was also investigated, at different temperatures, pH and incubation times. Results: The bacteriocin of B. subtilis showed great antimicrobial activity against S. pyogenes, followed by S. typhi and P. aeruginosa. However, the lowest antimicrobial activity was against A. baumannii. With the increase in the incubation time and temperature, the antimicrobial activity of bacteriocin was decreased, indicating the protein nature of bacteriocin. Compared to the standard antibiotics, the bacteriocin isolated from B. subtilis demonstrated a significant inhibitory effect against the tested pathogens. Conclusions: From this study, it can be concluded that bacteriocin can become a potential alternative to standard available medicines. They can be used against antimicrobial-resistant pathogenic bacteria because of their significant inhibitory activity against the tested pathogens compared to the standard antibiotics.