Article Figures & Data
Figures
- FIG. 1.
Etest antibiograms of PAO1 and PAOΔmutS with ceftazidime, imipenem, meropenem, ciprofloxacin, and tobramycin.
- FIG. 2.
Disk diffusion antibiograms of PAOΔmutS and PAO1 with ceftazidime (CAZ), imipenem (IPM), meropenem (MEM), ciprofloxacin (CIP), and tobramycin (TOB).
- FIG. 3.
Distributions of MICs of ceftazidime, imipenem, meropenem, ciprofloxacin, and tobramycin. White bars, percentages of nonhypermutable isolates; black bars, percentages of hypermutable isolates considering resistant mutant subpopulations; gray bars, percentages of hypermutable isolates without considering mutant subpopulations.
Tables
- TABLE 1.
MICs for and inhibition zone diameters of strains PAO1 and PAOΔmutS and their respective resistant mutant subpopulations
Antibiotic PAO1a PAOΔmutSa NCCLS breakpointsc Etest MIC (μg/ml) Disk diffusion diam (mm) Etest Disk diffusion N, R MIC (μg/ml) R, N diam (mm) MIC (μg/ml) MIC for the subpopulation (relative no.)b Diam (mm) Diam of the subpopulation (relative no.) Ceftazidime 1 25.6 1 48 (+++) 25.4 14.1 (+++) ≤8, ≥32 ≤14, ≥18 Imipenem 1.5 21.9 1.5 12 (+ to ++) 22.8 14.8 (++) ≤4, ≥16 ≤13, ≥16 Meropenem 0.38 29.4 0.5 3 (++) 27.2 19.0 (++) ≤4, ≥16 ≤13, ≥16 Ciprofloxacin 0.064 32.4 0.064 0.38 (++) 34.0 29.6 (++) ≤1, ≥4 ≤15, ≥12 Tobramycin 1.5 20.0 2 3 (+) 18.0 15.0 (+) ≤4, ≥16 ≤12, ≥15 ↵ a Results shown are the median values of five independent determinations. MICs and inhibition zone diameters were measured at 24 h for the general population and at 36 h for the resistant mutant subpopulation. The highest MICs or the smallest inhibition zone diameters of resistant mutant subpopulations are listed.
↵ b Relative number of resistant mutant colonies (see Materials and Methods). +, < 10 mutants; ++ 10 to 100 mutants; +++, > 100 mutants.
↵ c N, nonsuceptibility breakpoint; R, resistance breakpoint.
- TABLE 2.
Numbers of nonhypermutable or hypermutable isolates for which resistant mutant subpopulations were observed for each antibiotic
Antibiotic No. of isolates with resistant mutants subpopulations observed/no. tested bya: Etest Disk diffusion Nonhypermutable isolates (n = 25) Hypermutable isolates (n = 10) Nonhypermutable isolates (n = 25) Hypermutable isolates (n = 10) Ceftazidime 3/25 9/9 2/25 9/9 Imipenem 2/25 8/8 4/25 9/9 Meropenem 3/25 10/10 5/25 10/10 Ciprofloxacin 2/25 9/10 1/25 8/10 Tobramycin 1/24 6/10 1/24 7/10 ↵ a Isolates for which the MIC was higher than the highest concentration on the Etest strips were excluded (see Materials and Methods).
- TABLE 3.
Numbers of antibiotics for which mutants were detected in nonhypermutable or hypermutable isolates
Type of isolates (n) Test No. of antibiotics for which mutants were detected/no. tested ≥1 ≥2 ≥3 ≥4 5 Hypermutable (10) Etest 10/10 10/10 10/10 9/10 3/10 Disk diffusion 10/10 10/10 10/10 9/10 2/5 Nonhypermutable (25) Etest 9/25 3/25 0/25 0/25 0/25 Disk diffusion 9/25 5/25 0/25 0/25 0/25 - TABLE 4.
Antibiotic susceptibility percentages and mean MICs and inhibition zones diameters of nonhypermutable isolates, hypermutable isolates, and hypermutable isolates considering resistant mutant subpopulations
Antibiotic Nonhypermutable isolates (n = 25)a Hypermutable isolates (n = 10)a Hypermutable isolates + subpopulations (n = 10)a,b NCCLS breakpointsc % S by Etest/dd Mean Etest/MIC (μg/ml) Mean dd diam (mm) % S by Etest/dd Mean Etest/MIC (μg/ml) Mean dd diam (mm) % S by Etest/dd Mean Etest/MIC (μg/ml) Mean diam, dd (mm) N, R MIC (μg/ml) R, N diam (mm) Ceftazidime 96/96 1.3 28.4 60/70 8.4 19.9 10/10 129.7 7.6 ≤8, ≥32 ≤14, ≥18 Imipenem 100/96 1.1 22.1 50/60 6.3 15.6 10/10 28.2 9.1 ≤4, ≥16 ≤13, ≥16 Meropenem 100/100 0.1 36.5 100/100 0.4 29.7 60/80 1.7 20.8 ≤4, ≥16 ≤13, ≥16 Ciprofloxacin 92/92 0.3 27.4 20/20 1.9 17.5 20/20 7.9 11.6 ≤1, ≥4 ≤15, ≥21 Tobramycin 84/72 2.4 15.9 90/70 3.4 16.7 70/50 4.5 12.6 ≤4, ≥16 ≤12, ≥15
