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Antimicrobial activity of recombinant Clostridium butyricum Miyairi bacteriocin against Clostridioides difficile

Rivet-Tissot, Jessalyn
Clostridioides difficile (C. difficile) is a Gram positive, spore forming, toxin-producing and anaerobic commensal bacterium. It is the leading cause of nosocomial antibiotic associated diarrhea in hospital and nursing homes. It is a worldwide bacterium spread through spores found in animals, soil, water, and food causing mild to severe colitis and in some cases leading to sepsis. C. difficile is antibiotic resistant and currently treated with metronidazole and vancomycin. As more pathogens become resistant to antibiotics, it is important to find novel alternatives for treatment. Bacteriocins are small peptides produced by bacteria which exhibit antimicrobial activity against closely related types of bacteria. Clostridium butyricum Miyairi bacteriocin (CBMB) is produced by a probiotic strain of Clostridium butyricum 588 made in Japan to treat diarrhea. Previously, we demonstrated that recombinant CBMB has antimicrobial activity against C. difficile strain R20291, a common laboratory strain. The aim of this research was to assess antimicrobial activity of CBMB against different C. difficile environmental isolates collected from Taiwan by our laboratory. Assays were performed to evaluate and compare growth rate with CBMB and vancomycin, minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and germination efficiency. Although growth curves showed significantly different growth rates among C. difficile environmental isolates, MICs and MBCs values were similar. CBMB had similar MICs and MBCs on toxigenic and non-toxigenic isolates of C. difficile as well. MIC and MBC assays performed on other bacteria confirmed that CBMB is a low spectrum bacteriocin as it only had inhibitory activity for some bacteria at high concentrations. CBMB was also shown to reduce spore germination at high concentrations. In summary, CBMB could be a potential treatment for C. difficile infection (CDI) in the future.