C. difficile antimicrobial treatment, illustration. Bacteriocin being used to kill a C. difficile bacterium, by injection across the cell membrane by a bacteriophage-like mechanism. Bacteriocins are toxins that can kill bacteria. C. difficile is a rod-shaped bacterium that causes pseudomembranous colitis, one of the most common hospital-acquired infections, and antibiotic-associated diarrhoea. Infection can be fatal. This bacterium has become increasingly resistant to normal antibiotics, and research into new defences includes the use of bacteriocins.