1 × 10-7 LVX: Levofloxacin; CIP: Ciprofloxacin; PRU: Prulifloxacin; Cmax: peak plasma concentration; Cmin: trough plasma concentration * Frequency of mutations was calculated only for

strains with MIC < Cmin. Table 2 Fluoroquinolone activity on strains grown after single step selection in E. coli and Klebsiella spp. at plasma concentrations Drug MIC range (mg/L)/number of strains grown   E. coli (n = 20) Klebsiella spp . (n = 20)   Cmax Cmin* Cmax Cmin* LVX 500 mg -/0 1/1 -/0 0.5 - 4/16 LVX 750 mg -/0 1 - 4/2 -/0 1 - 8/14 CIP 500 mg -/0 0.25 - 0.5/4 -/0 0.125 - 4/20 PRU 600 mg 2 - 4/3 0.25 - 2/5 4 - 8/5 0.06 - 1/20 LVX: Levofloxacin; CIP: Ciprofloxacin; PRU: Prulifloxacin; Cmax: peak plasma concentration; Cmin: trough plasma concentration * MICs were evaluated for all the tested strains Multi-step selection of resistant bacteria Table 3 shows the total Epoxomicin manufacturer number of strains grown after multi-step selection and MIC values after 1, 5 and 10 passages on antibiotic-gradient plates and after the subsequent 10 passages on antibiotic-free medium. After multi-step selection, a general increment in MICs was observed for all microrganisms with all tested antibiotics; no selection of resistance was observed with levofloxacin at 750 mg in E. coli and no selection of resistance Caspase Inhibitor VI cell line was observed with levofloxacin (both

doses) in Klebsiella spp. at plasma concentration of fluoroquinolones Drug MIC (mg/L): median (range)   Nr of strains Pre-sel I STEP V STEP X STEP X STEP free E. coli (n = 20) LVX

500 mg 7 0.5 (0.5 – 1) 2 (0.5-4) 4 (1 – 8) 8 (2 – 8) 4 (1 – 8) LVX 750 mg 0 0.016 – 1 n.d. n.d. n.d. n.d. CIP 500 mg 8 0.25 (0.125 – 0.5) 0.5 (0.125 – 1) 2 (2 – 4) 8 (4 – 16) 4 (1 – 8) PRU 600 mg 12 0.064 (0.016 – 0.125) 1 (0.5 – 4) 2 (2 – 4) 4 (2 – 8) 4 (2 – 8) Klebsiella spp. (n = 20) LVX 500 mg 0 0.03 – 1 n.d n.d n.d n.d Exoribonuclease LVX 750 mg 0 0.03 – 1 n.d n.d n.d n.d CIP 500 mg 11 0.06 (0.03 – 0.5) 0.5 (0.5 – 1) 2 (1 – 8) 8 (4 – 16) 4 (1 – 4) PRU 600 mg 16 0.06 (0.03 – 0.25) 0.5 (0.06 – 1) 2 (0.25 – 16) 4 (0.5 – 32) 4 (0.25 – 16) LVX: Levofloxacin; CIP: Ciprofloxacin; PRU: Prulifloxacin; Pre-sel: MICs before starting multi-step selection of resistance; I Step: MICs after the first passage on antibiotic gradient agar plates; V Step: MICs after the fifth passage on antibiotic gradient agar plates; X Step: MICs after the last passage on antibiotic gradient agar plates; X step free: MICs after ten subcultures on antibiotic free agar plates. After 10 passages on antibiotic gradient plates and 10 subcultures in antibiotic-free medium, the highest number of strains with MIC higher than the resistance breakpoint was found for selleck chemicals ciprofloxacin and prulifloxacin both in E. coli (5 and 7 strains, respectively) and Klebsiella spp. (6 and 8 strains, respectively).