A note: ortho-phthalaldehyde: proposed mechanism of action of a new antimicrobial agent.

Ortho-phthalaldehyde (OPA) is a new aromatic dialdehyde antimicrobial agent, the mechanism of action of which has been little studied. The aims of this paper are to examine what is currently known about its mechanism of action, to compare the action with that of a widely investigated aliphatic dialdehyde, glutaraldehyde (GTA), and to put forward a hypothesis that would, in the light of current knowledge, explain how OPA inactivates micro-organisms, including GTA-resistant Mycobacterium chelonae.