Table 1.

Antimicrobial susceptibilities of 41 antimicrobials against 99 S. maltophilia strains with different PFGE profiles

Antimicrobial agent (inhibitor concn [μg/ml])MIC (μg/ml)a% of resistant strainsb
Range50%90%
Ampicillin64–>1,0241,024>1,024NAc
Amoxicillin-clavulanate≤4–>1,0241,024>1,024NA
Ticarcillin2–>1,024512>1,02473.7
Ticarcillin-clavulanate (2)0.5–>1,02464>1,02446.5
Piperacillin4–>1,024256>1,02463.6
Piperacillin-tazobactam (4)2–>1,0241281,02454.5
Cefotaxime0.5–>1,0246451261.6
Ceftazidime0.06–1,0241625649.5
Cefpirome1–512128256NA
Cefepime0.12–2563212853.5
Moxalactam0.03–2562322.0
Aztreonam2–>1,024256>1,02491.9
Aztreonam-clavulanate (2)0.25–>1,0241281,02465.7d
Imipenem4–>1,024512>1,02499.0
Meropenem1–1,0246425687.9
Gentamicin0.25–>25664>25680.8
Tobramycin0.25–>25664>25676.7
Kanamycin2–>256256>256NA
Amikacin0.25–>256256>25680.8
Netilmicin0.25–25612825677.7
Erythromycin16–>256128256NA
Clarithromycin16–>256128256NA
Azithromycin2–>12864128NA
Tetracycline0.5–128326485.8
Doxycycline0.06–16121.0
Minocycline≤0.01–20.210
Nalidixic acid0.06–256432NA
Norfloxacin0.06–256166455.6
Pefloxacin≤0.01–6414NA
Ofloxacin≤0.01–640.545.0
Ciprofloxacin≤0.01–640.5413.1
Levofloxacin≤0.01–320.223.0
Sparfloxacin≤0.01–80.10.5NA
Grepafloxacin≤0.01–160.11NA
Gatifloxacin≤0.01–160.113.0
Moxifloxacin≤0.01–320.10.5NA
Clinafloxacin≤0.01–40.10.5NA
Trovafloxacin≤0.01–32≤0.010.5NA
Chloramphenicol2–128166435.4
Fosfomycin32–>256128256NA
Trimethoprim-sulfamethoxazole0.1/1.9–>608/3238/2608/3227.3
  • a 50% and 90%, MIC50 and MIC90, respectively.

  • b Susceptibility rates were calculated according to the NCCLS proposed breakpoints for P. aeruginosa and nonmembers of the familyEnterobacteriaceae.

  • c NA, no available NCCLS criteria.

  • d The NCCLS breakpoint for aztreonam was used for aztreonam-clavulanate.