Figure 11.

Lack of tolerance development upon sub-lethal aPDI/aBL treatment in recA-deficient S. aureus mutant. Overnight JE2 SE805 cultures (5 × 10⁷ CFU/ml) were incubated with 0.1 μM RB and illuminated with 515 nm light at a dose of 2 J/cm². Following exposure, 10 μL aliquots of the treated samples were taken to determine the survival rate. The rest of the sample was centrifuged and washed with PBS. Fifty microliters of the samples was transferred into fresh TSB medium (5 mL) to re-grow overnight. The next day, the treatment was repeated under the same conditions. The cycle of exposure - regrowth - exposure was repeated 5 times. In case of aBL treatment, overnight cultures were irradiated with 411 nm light dose of 50 J/cm². The susceptibility of S. aureus to RB-aPDI was investigated upon 1 (panel A) and 5 (panel B) cycles of sub-lethal RB-aPDI, and susceptibility of S. aureus to aBL was investigated upon 1 (panel C) and 5 (panel D) cycles of sub-lethal aBL. The detection limit was 100 CFU/ml. The values are the means of three separate experiments. Error bars represent standard deviation (SD).