FIG 1.

Robustness of collateral sensitivity to tobramycin and aztreonam in clinical isolates of P. aeruginosa subjected to short-term ALE on ciprofloxacin. Resistance to ciprofloxacin and CS to aztreonam or tobramycin were analyzed in 25 clinical isolates, 4 replicate populations each (100 populations)—indicated as 1, 2, 3, or 4—subjected to ALE in the presence of ciprofloxacin for 3 days. Since control populations evolved in the absence of antibiotic (100 populations) may present subtle changes (below or above a 2-fold increase or decrease) in their susceptibility to antibiotics with respect to the MIC of parental strains, only changes in MICs above or below a 2-fold increase or decrease were considered biologically relevant to classify a population as resistant (purple) or susceptible (yellow). MIC values (in micrograms per milliliter) of all the evolved populations are included in Table S1. MIC values (in micrograms per milliliter) of control populations evolved in the absence of drugs are included in Table S2. Log₂ fold change MIC values are indicated. When evolved populations contained different subpopulations presenting diverse MICs, the MIC with a greater change from the parental strain is represented. Each column contains the log₂ fold change MIC for each antibiotic in every replicate population. TOB, tobramycin; CIP, ciprofloxacin; ATM, aztreonam; ND, fold change could not be calculated because MICs were above the limit of detection.