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. 2022 Aug 24;10(5):e00723-22. doi: 10.1128/spectrum.00723-22

TABLE 2.

Overview of the effects of ciprofloxacin risk concentration on P. aeruginosa clinical isolates and its association with their 3-day sub-MIC selective windowsa

Phenotypic changes upon exposure to 0.04 μg/mL of CIP (fold-changes)
Strain Relative CIP MSC (3 days) CIP mIC of the parental strains Fitnessb 3-day evolved populations
CIP mICc Mutant selectionc
Biofilm formationc Elastase activityc Pyocyanin productionc Swarming motilityc Cross-resistanced
MIC 2×MIC
Narrow sub-MIC selective window
 GAL02-002 1/2 MIC 0.25 1.0 2.4 30 2.3 1.3 0.8 1.1 2.2 None
 FQSE111010 1/5 MIC 0.25 1.0 1.4 3.6 1.3 1.0 1.0 1.1 1.0 None
 FQSE06-0403 1/5 MIC 0.19 1.0 5.4 1.7 × 109 1.2 × 109 1.7 1.0 0.9 0.9 LEV, CAZ, AMK, FOF
 CAT02-004 1/10MIC 0.25 0.9 2.3 9.7 × 104 4.6 × 107 0.9 1.2 0.7 4.4 None
Wide sub-MIC selective window
 CLE03-004 1/25MIC 0.094 0.3 13.3 2.1 × 104 7.9 × 104 1.3 1.0 0.8 1.1 LEV, AMK, ATM
 ICA01-004 1/25MIC 0.064 0.6 13.9 7.7 × 105 9.3 × 105 0.9 0.9 0.9 0.3 LEV, CAZ, AMK, ATM, IPM
 AND04-004A 1/25MIC 0.064 0.5 10.4 1.6 × 107 2.6 × 108 1.0 0.4 1.0 0.1 LEV, IPM
 CAN01-002 1/25MIC 0.094 0.9 7.8 3.9 × 105 1.6 × 107 0.8 0.3 0.8 0.9 LEV
 BAL04-002 1/50MIC 0.094 0.4 10.0 5.5 × 105 3.3 × 106 1.1 1.0 1.0 0.8 LEV, CAZ, ATM, FOF
 FQSE11-0603 1/50MIC 0.125 1.1 13,5 1.7 × 105 1.7 × 106 1.0 1.1 0.9 1.1 LEV
 PA14 1/200MIC 0.064 0.6 23.7 8.6 × 104 9.1 × 104 0.6 0.8 0.7 0.2 LEV
a

The table summarizes the changes in phenotypic traits of the strains used in this study after 3 days in the presence of ciprofloxacin sub-MIC risk concentration. A statistically significant fold-change in a parameter (excepting CIP MIC fold-change) is highlighted in bold. An MSC of 1/2 of MIC to 1/10 of MIC is dubbed narrow sub-MIC selective window, whereas 1/25 of MIC to 1/200 of MIC is dubbed wide sub-MIC selective window. CIP, ciprofloxacin; LEV, levofloxacin; CAZ, ceftazidime; AMK, amikacin; ATM, aztreonam; IPM, imipenem; FOF, fosfomycin.

b

This parameter is measured as the average fold-change of the strain’s fitness in the presence of 0.04 μg/mL of ciprofloxacin for 30 h, with respect to the one in LBB for the same interval.

c

This parameter is measured as the average fold-change of the value of populations evolved under 0.04 μg/mL of ciprofloxacin for 3 days, with respect to the ones evolved in LBB for the same interval.

d

At least half the replicates must show ≥2-fold of the parental strain MIC to the antibiotic, as determined using MIC test strips that discern small differences, to be subsumed as a cross-resistance.