Antibiotic susceptibility percentages and mean MICs and inhibition zones diameters of nonhypermutable isolates, hypermutable isolates, and hypermutable isolates considering resistant mutant subpopulations

AntibioticNonhypermutable isolates (n = 25)aHypermutable isolates (n = 10)aHypermutable isolates + subpopulations (n = 10)a,bNCCLS breakpointsc
% S by Etest/ddMean Etest/MIC (μg/ml)Mean dd diam (mm)% S by Etest/ddMean Etest/MIC (μg/ml)Mean dd diam (mm)% S by Etest/ddMean Etest/MIC (μg/ml)Mean diam, dd (mm)N, R MIC (μg/ml)R, N diam (mm)
Ceftazidime96/961.328.460/708.419.910/10129.77.6≤8, ≥32≤14, ≥18
Imipenem100/961.122.150/606.315.610/1028.29.1≤4, ≥16≤13, ≥16
Meropenem100/1000.136.5100/1000.429.760/801.720.8≤4, ≥16≤13, ≥16
Ciprofloxacin92/920.327.420/201.917.520/207.911.6≤1, ≥4≤15, ≥21
Tobramycin84/722.415.990/703.416.770/504.512.6≤4, ≥16≤12, ≥15
  • a S, percentage of strains susceptible according to NCCLS breakpoints by the Etest and by disk diffusion (dd). Means are geometric means.

  • b Resistant mutant subpopulations were considered for these values.

  • c N, nonsusceptibility breakpoint; R, resistance breakpoint.