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