Figure 4.

The ethidium bromide (EtBr) agar cartwheel method applied to tested bacterial strain, MRSA (up), E. faecalis (right), and P. aeruginosa (down) on agar plates contained different concentrations of EtBr (A) 0 µg/mL, (B) 1 µg/mL, and (C) 2 µg/mL. Only P. aeruginosa retained EtBr and was fluorescence after exposure to UV light due to a lack of the efflux mechanism contrary to the absence of fluorescence in both MRSA and E. faecalis, due to the presence of efflux mechanism in these bacterial strains resulting in complete efflux of EtBr.