Exotoxin and Endotoxin: Bacterial Metabolic Product

Difference between Exotoxin and Endotoxin

There are two types of toxin produced by bacteria.

1. Endotoxin
2. Exotoxin


  • Endotoxin lipopolysaccharide binds to neutrophil and delta neutrophil function by decreasing chemotactic activity and migration and also alter the bactericidal property of neutrophils.
  • Endotoxin cannot destroy by autoclave.
  • Endotoxins antigenic and cannot be toxoid so that they can not be utilized by antibodies.

Difference between Exotoxin and Endotoxin



Protein/polypeptide molecular weight 10000 to 1900000

Lipopolysaccharide in nature

Hear liable (destroyed > 60 oC 

Heat stable 


Actively secreted/diffuse by living bacterial cell into surrounding medium 

Form integral part of the cell wall so released only on disruption of bacterial cell

Exotoxins are highly antigenic so that they stimulate formation of antitoxin which neutralizes toxins.

Very weak antigenic so antitoxin is not formed but antibodies against polysaccharide are raised

Toxins are  converted into toxoid by formaldehyde.

Can not be toxoided

Enzymatic in nature

No enzymatic action

Exotoxin produces specific pharmacological effect for each exotin

Non-specific action to all endotoxins

Very high potency

Low potency 

highly specific for particular tissue example tetanus toxin for CNS 

Non-specific in action

Prepared by ThePharmapedia.com

Exotoxin do not produce fever in host

Endotoxin usually produce fever

Exotoxins are produced mainly by gram-positive bacteria and also by some gram-negative bacteria

Endotoxins are mainly produced by gram-negative bacteria

 Prepared by ThePharmapedia.com

Exotoxin, Bacteria, Metabolic Product, Pharmapedia, The Pharmapedia

Exotoxin are Actively secreted/diffuse by living bacterial cell into the surrounding medium following lysis.

Examples of endotoxin-producing bacteria are: Salmonella typhi (Typhoid), Vibrio cholerae (Cholera). Streptococcus pneumoniae (sepsis)

Endotoxin, Pharmapedia, The Pharmapedia

Endotoxins are an integral part of the cell wall and released only on disruption of a bacterial cells.

Examples of exotoxin producing bacteria are:Clostridium botulinum (Botox), Clostridium tetani (Tetanus), Corynebacterium diphtheriae (Diphtheria).

Multiple Choice Question (MCQ)
Q1. Which toxin can be converted into toxoid by formaldehyde?

a. Exotoxin

b. Endotoxin

c. Both

d. None

Ans: A

Q2. The chemical nature of endotoxin is

a. Lipopolysaccharide

b. Protein

c. Carbohydate

d. None of these

Ans: A

Q3. ………………….is the toxin produced inside the bacteria itself as a part of their metabolism?

a. Exotoxin

b. Endotoxin

c. Both

d. None

Ans: A


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