- A toxin produced by certain bacteria and released upon destruction of the bacterial cell.
- A toxic substance set free during the process of bacteriolysis by means of immune sera against which the animal body does not appear to be capable of producing an antitoxin. These specific toxins are only liberated after or during the destruction of the microorganism.
- Any <xref>toxin</xref> secreted by a <xref>microorganism</xref> and released into the surrounding environment only when it dies.
- a toxin that is confined inside the microorganisms and is released only when the microorganisms are broken down or die