High intensity lethal photosensitization of Staph. aureus □, Strep. pyogenes ▨ with 25 μg ml-1 ICG and P. aeruginosa ■ with 200 μg ml-1 ICG. An equal volume of either 50 μg ml-1 (in the case of Staph. aureus and Strep. pyogenes) or 400 μg ml-1 (in the case of P. aeruginosa) ICG (L-S+ and L+S+) or PBS (L-S- and L+S-) was added to each bacterial suspension. Samples were left in the dark for 30 minutes and then (L+S- and L+S+) irradiated at a fluence rate of 1.37 W cm-2 for 1, 3 or 5 minutes with light from a NIR 808 nm laser, corresponding to light doses of 82, 247, or 411 J cm-2 respectively. Samples L-S+ and L-S- were kept in the dark.