Fig 1.
Antibiotics induced accumulation of PYO.
(A) Representative images of Kan-induced color changes in P. aeruginosa PAO1 cultured in LB medium, with shaking of 200 r/min at 37°C. The image of the tubes was taken at 12 h. (B) PYO concentrations and cell densities (A600 nm) of PAO1 in varying concentrations of Kan after incubation in the tubes for 12 h. Regarding A and B, bacteria in the presence and absence of Kan are in the exponential phase and early stationary phase, respectively. (C) Typical dynamics of PYO concentrations (left) and bacterial growth curves (right) of PAO1 treated with 20 μg/mL Kan in the tubes, with shaking of 200 r/min at 37°C. The data underlying this figure can be found in S1 Data. Means ± SD are presented (n = 3). *P < 0.05, **P < 0.01, ***P < 0.001. P values were determined by paired t test. A600 nm, absorbance 600 nm; Kan, kanamycin; LB, Luria-Bertani; PYO, pyocyanin.
Fig 2.
PYO-mediated tolerance against antibiotic treatments.
(A) PYO-mediated tolerance in P. aeruginosa PAO1. PAO1 in the presence of 2 μg/mL PYO was treated with various antibiotics, including 50 μg/mL Kan, 4 μg/mL gentamicin, 20 μg/mL streptomycin, 20 μg/mL tobramycin, 0.5 μg/mL norfloxacin, 7.5 μg/mL chloramphenicol, 50 μg/mL carbenicillin, and 1.0 μg/mL polymyxin B. All data were plotted from the growth curves of various bacterial species at 10 h. Means ± SD are presented (n = 3). (B) PYO-mediated tolerance in gram-negative bacteria, including P. aeruginosa PAO1, Escherichia coli (MG1655- and ESBL-expressing strain), and Salmonella typhimurium, and gram-positive bacteria, including Bacillus cereus, B. subtilis, and Staphylococcus aureus. Bacteria were cultured in LB media supplemented with 20 μg/mL streptomycin, except 5 μg/mL streptomycin for B. cereus. Means ± SD are presented (n = 6). The data underlying this figure can be found in S1 Data. *P < 0.05, **P < 0.01, ***P < 0.001; P values were determined by paired t test. A600 nm, absorbance 600 nm; ESBL, extended-spectrum beta-lactamase; Kan, kanamycin; LB, Luria-Bertani; PYO, pyocyanin.