FIG 3.

Cigarette smoke exposure induces MRSA surface changes, including a less negative surface charge and increased hydrophobicity, leading to increased adherence and invasion of epithelial cells. (A) CSE-MRSA binds less of cationic PLL-FITC, consistent with alteration in surface charge (less negative = more positive surface charge) in response to CSE exposure, in a dose-dependent manner. (B) Background fluorescence (no PLL added) was equal among groups. CSE precipitate alone had no impact on surface charge, with equivalent surface binding of 2 μM PLL as control MRSA. However, 24-h-old CSE induced a 2-fold shift in surface charge, but not the 12-fold shift induced by freshly made CSE. (C) Nicotine alone induced shifts in MRSA surface charge leading to less PLL-FITC binding (5-fold by 3 mg and 11-fold by 6 mg), consistent with nicotine contributing to CSE-induced surface charge changes. (D) Surface charge changes induced by CSE exposure persisted after passage into THB two times, for 24 h after exposure, and repetitive daily exposures for 3 and 4 days further enhanced surface charge changes. (E) S. aureus strain SA113 had similar changes in PLL-FITC binding upon exposure to CSE. (F) Exposure to CSE induced increasing hydrophobicity in a dose-dependent manner, as evidenced by fewer bacteria recovered from the aqueous phase as the CSE concentration was increased. (G and H) CSE exposure increased adherence of MRSA to epithelial cells (G) and increased MRSA invasion of and persistence within epithelial cells (H). *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.