FIG 2.

Antibiotic treatment sensitizes mice to HA-MRSA infection. (A) C57BL/6J mice were preexposed to metronidazole (1 g/L), vancomycin (0.5 g/L), ampicillin (1 g/L), and neomycin (0.5 g/L) in their drinking water for 2 weeks and switched to antibiotic-free water 1 day prior to challenge. (B to D) Survival curves of intranasal infection with 4 × 10⁸ CFU of LAC (B), TH16 (C), and BS_4884 (D) (n = 8 to 18 mice/group). (E) Bacterial burden at 4 h postinfection in the lung and peripheral organs of mice infected with TH16 (n = 4 to 5 mice/group). (F) H&E staining of two representative histological sections of lung tissue 18 h after infection with 1 × 10⁸ CFU of TH16. (G and H) Flow cytometry analysis of lung tissue 18 h after infection with1 × 10⁸ CFU of TH16 (G) and prior to infection (H). Neutrophils were gated as live, single, TCRβ⁻ B220⁻ CD45⁺ Ly6G⁺ CD11b⁺ cells. Statistical analysis was performed using a log rank (Mantel-Cox) test (B to D), two-way ANOVA with a Šídák posttest (E), and Student’s t test (G and H). *, P < 0.05; **, P < 0.01; ***, P < 0.001.