Gram-Positive Bacilli: Corynebacterium, Bacillus and Clostridium

Key points

• • Many of these gram-positive rods cause disease largely through powerful toxins, though some also spread and invade tissues.
• • Corynebacterium diphtheriae causes diphtheria: its toxin kills throat cells to form a grey false membrane and can damage the heart and nerves.
• • Bacillus anthracis causes anthrax, forms spores, and is a large gram-positive rod that can affect the skin, lungs or gut depending on how it is caught.
• • Clostridia are anaerobic, spore-forming rods: Clostridium tetani causes tetanus (a locked-jaw muscle spasm) through a toxin that blocks muscle relaxation.
• • Clostridium botulinum causes botulism, a floppy paralysis, through a toxin that blocks the nerve signal to muscle; it is classically caught from improperly canned food, but also as wound and infant botulism.
• • Clostridium perfringens causes gas gangrene, while Clostridioides difficile causes a serious bowel infection after antibiotics disturb the normal gut flora.