Killing of methicillin-resistant Staphylococcus aureus in vitro using aluminium disulphonated phthalocyanine, a light-activated antimicrobial agent.

The aim of this study was to determine whether 16 epidemic methicillin-resistant strains of Staphylococcus aureus (EMRSA) could be killed by the light-activated antimicrobial agent aluminium disulphonated phthalocyanine (AIPcS2). EMRSA suspensions were irradiated with light from a laser diode in the presence of AIPcS2 and survivors enumerated. All strains were susceptible to killing, the bactericidal effect being dependent on the AIPcS2 concentration and the light dose. AIPcS2 rendered the bacteria light-sensitive almost immediately and killing was unaffected by the growth phase of the organism. Scavengers of singlet oxygen and free radicals protected the bacteria from killing. These results imply that light-activated antimicrobial agents may be useful in eliminating EMRSA from wounds or carriage sites.