Table 1.

Growth of recovered P. aeruginosa isolates in ASM with colistin.

Time (h)	MIC (µg mL−1) of colistin against isolates collected from mono-species culture challenged with:
	2× MIC colistin				5× MIC colistin
1	25	45	>1000	>1000	20	25	45	45
8	20	45	>1000	>1000	20	25	20	20
24	20	20	20	20	20	20	20	20
48	20	20	20	20	20	20	20	20
	MIC (µg mL−1) of colistin against isolates collected from polymicrobial co-culture challenged with:
	2× MIC colistin				5× MIC colistin
1	45	45	>1000	>1000	20	20	25	45
8	45	>1000	>1000	>1000	25	25	45	45
24	25	45	>1000	>1000	20	20	25	25
48	20	20	20	20	20	20	20	20

Number of P. aeruginosa PAO1 isolates able to grow in ASM containing the indicated concentration of colistin (in µg mL⁻¹). Four isolates were collected at each time point (1 h, 8 h, 24 h and 48 h) after challenge of each culture with 2× or 5× MIC colistin (i.e., 4 × 4 × 2 = 32 isolates in all). Isolates were randomly selected from agar spreads of appropriately diluted single-species (upper panel) or PA/SA/CA mixed-species (lower panel) steady-state continuous-flow cultures. The ability of each isolate to grow in different concentrations of colistin was then determined. The results were confirmed over three independent experiments using fresh batches of ASM. Shades of grey indicate resistance to colistin relative to WT; dark grey < light grey < white.