FIGURE 3.

Efficacy of “early” treatment with tobramycin (TOB) (a, c, e, g) and colistin (COL) (b, d, f, h) against Pseudomonas aeruginosa MDR-RP73 in a murine model of chronic lung infection. C57BL/6 male mice (aged 8–10 weeks) were infected with 5×10⁵ colony-forming units (CFUs) of MDR-RP73 embedded in agar beads by intratracheal inoculation. Treatment was started 5 min after infection, with 16 mg·kg⁻¹ TOB, 1 mg·kg⁻¹ COL or vehicle administered daily for 7 days via an aerosoliser (aero). Alternatively, 160 mg·kg⁻¹ TOB, 10 mg·kg⁻¹ COL or vehicle was administered via the subcutaneous (s.c.) route. a, b) Before each administration, mice were weighed, and the percentage change from the initial body weight was averaged for each group of mice. Data are presented as mean±sem. c–h) At day seven post-infection, mice were killed, bronchoalveolar lavage fluid (BALF) was collected and lungs were excised, homogenised and plated onto tryptic soy agar to determine the bacterial burden (c, d). Each dot represents CFUs per lung from one mouse, and horizontal lines represent the median values. e, f) Total cell and g, h) neutrophil counts were performed in BALF. Data are presented as the mean±sem pooled from two independent experiments (n=11–16). *: p<0.05; **: p<0.01; ***: p<0.001; ****: p<0.0001.