Figure 1

Nicotine induced biofilm formation in Staphylococcus aureus. (A) Clinical S. aureus strains were exposed to various concentrations of nicotine (0, 0.1, 0.2, 0.5, 1, 2 mg/mL). Crystal violet staining of biofilm-associated biomass revealed that the biofilm formation was increased in all strains in response to nicotine treatment. (B) A dose-dependent increase in biofilm formation was observed in USA300. Maximal biofilm formation was observed at 2 mg/mL. (C) Representatives of confocal images showed that denser biofilms were formed in the nicotine-treated group than in the control group. (D) The average thickness of biofilms in nicotine treatment group was 16.90 ± 0.66 μm (n = 3), while the thickness in the untreated group was 12.67 ± 0.91 μm (n = 3) (p < 0.05). (E) S. aureus USA300 strain FPR3757 growth curves under different concentrations of nicotine (0, 0.1, 0.2, 0.5, 1, 2 mg/mL) were determined by measuring the OD at a wavelength of 600 nm at 1-h intervals for 12 h. *P < 0.05 compared with untreated group. CI, clinical isolates.