Table 1 Growth of recovered P. aeruginosa isolates in ASM with colistin.

From: Decreased efficacy of antimicrobial agents in a polymicrobial environment

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

  1. 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.