Lethal photosensitisation of EMRSA-16 with 1, 5, 10 and 20 μM methylene blue and a 665 nm laser light dose of 1.93 J/cm2. An equal volume of either PBS (S-) or methylene blue (S+) (concentrations ranging from 1-20 μM) was added to 50 μL of the bacterial suspension and either kept in the dark (L-) (white bars) or exposed to 665 nm laser light with an energy density of 1.93 J/cm2 (L+) (black bars). After irradiation/dark incubation, samples were serially diluted and the surviving CFU/mL enumerated. Error bars represent the standard deviation from the mean. *** P < 0.001 (Mann Whitney U test). Experiments were performed three times in triplicate and the combined data are shown.