Which toxin is present inside a bacterial cell and is released when the cell dies and the cell wall disintegrates, heat-stable?

• A. Endotoxin
• B. Exotoxin
• C. Neurotoxin
• D. Enterotoxin

Answer: (A)

Endotoxins are part of the outer membrane of Gram-negative bacteria, embedded in the cell wall as lipopolysaccharide. When the bacterium dies and the cell wall disintegrates, endotoxin is released into the surrounding environment. Its lipid A component is responsible for triggering fever and inflammatory responses, and endotoxin is relatively heat-stable, meaning it isn’t inactivated by the heat levels that typically denature many protein toxins. In contrast, exotoxins are secreted proteins produced by bacteria and are often heat-labile; neurotoxins and enterotoxins are specific exotoxins that affect the nervous system or gut rather than being released from lysed cells.