(A) MRSA and (B) E. coli aPDI killing using “in format” with increasing LC15 concentration, and either a fluence of 10 J/cm2 of 415 nm light or dark, and with or without addition of 100 mM NaNO2. (C) MRSA and (D) E. coli aPDI using “after format” where cells were added immediately after light to a mixture of increasing concentrations of LC15 mixed with 200 mM NaNO2, that had been illuminated with 0, 10, 20, or 40 J/cm2 of 415 nm light.