MICs (μg/ml) Antibiotic Chitosan (MW) AMK LEV TET High Moderate Low a MIC50 4.88 0.8 34.19 312.5 312.5 156.25 b MIC90 54.87 13.67 87 625 625 312.5   MIC range 1.22-312.5 0.15-39.06 1.17-150 78.13-625 78.13-625 78.13-312.5 c Species-related breakpoints (S≤/R>)  16/64 2/8 4/16 - - - aThe minimal concentration at which 50% of the isolates was inhibited bThe minimal concentration at which 90% of the isolates was inhibited cCLSI, 2007 [18]. AMK; Amikacin, LEV; Levofloxacin, TET; Tetracycline

Table 1: Comparative biostatic activity of the most effective antibiotics and different molecular weight chitosans against 42 P. aeruginosa isolates.