Efficacy and pharmacokinetics of tobramycin (TOB) (a, c, e, g) and colistin (COL) (b, d, f, h) in a mouse model of acute Pseudomonas aeruginosa airway infection. C57BL/6 male mice (aged 8–10 weeks) received intratracheal inoculations with 1×106 colony-forming units (CFUs) of planktonic PAO1. 5 min after infection, 2 mg·kg−1 TOB, 1 mg·kg−1 COL or vehicle was administered via an aerosoliser (aero) or the intranasal (i.n.) route. Alternatively, 20 mg·kg−1 TOB, 10 mg·kg−1 COL or vehicle was administered via the subcutaneous (s.c.) route. a–h) After 6 h, the mice were killed, bronchoalveolar lavage fluid (BALF) was collected, and the lungs were excised, homogenised and plated on tryptic soy agar to determine the bacterial burden (a, b). Each dot represents CFUs per lung from one mouse, and horizontal lines represent the median values. c, d) For pharmacokinetics analysis, mice were killed 5 min, 6 h and 24 h after treatment, and the concentration of antibiotics was measured in the lung and plasma (supplementary figure S1). The limits of quantification (LOQs) are indicated. e, f) Total cell and g, h) neutrophil counts were performed in BALF. Data are presented as mean±sem pooled from two independent experiments (n=7–8 for efficacy, and n=4–8 for pharmacokinetics). *: p<0.05; **: p<0.01; ****: p<0.0001.