FIGURE 3. Competitive selection against resistance in a suppressive drug combination.

From the following article:

Antibiotic interactions that select against resistance

Remy Chait, Allison Craney & Roy Kishony

Nature 446, 668-671(5 April 2007)



Doxycycline-sensitive (doxS) and doxycycline-resistant (doxR) strains, differentially tagged with CFP and YFP, were inoculated at a 1:1 ratio into an array of drug combinations (a, b, black dots). Final ratios, reflecting fitness differences (growth and death) between the strains, measured by FACS after 24 h, are shown for combination treatments of doxycycline–erythromycin (synergy, a) and doxycycline–ciprofloxacin (suppression, b) as indicated in the colour scale at the bottom right. Blank regions indicate no growth. Along a line of constant wild-type inhibition as measured in Fig. 2 (for example 70% inhibition, solid black line in b), increasing the doxycycline concentration can select against the resistant mutant even while maintaining inhibition of the wild type. ce, Sample FACS data at points indicated in b. The data are consistent across experimental replicates and CFP/YFP marker swaps (data not shown).

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