TABLE 2.
In vitro activities of comparators against 392 multiple-drug-resistant strains
| Organism and antimicrobial agent | MIC50 (μg/ml) | MIC90 (μg/ml) | MIC range (μg/ml) | % Susceptiblea |
|---|---|---|---|---|
| K. pneumoniae (98 isolates) | ||||
| Ampicillin | >32 | >32 | >32->32 | 0 |
| Amoxicillin-clavulanate (2:1) | >32b | >32b | 2->32b | 22.5 |
| Piperacillin-tazobactam (4 μg/ml) | >128b | >128b | 0.5->128b | 23.5 |
| Ceftriaxone | 64 | >64 | 0.06->64 | 17.3 |
| Ceftazidime | >32 | >32 | 8->32 | 6.1 |
| Cefepime | 32 | >32 | 0.5->32 | 29.6 |
| Imipenem | 4 | 16 | 0.25->16 | 59.2 |
| Levofloxacin | 8 | >8 | 0.03->8 | 19.4 |
| Amikacin | 8 | 32 | 0.5->64 | 91.8 |
| Ciprofloxacin | >32 | >32 | 0.12->32 | 11.2 |
| Minocycline | 2 | 8 | 0.5->16 | 64.3 |
| Colistin | 0.5 | 16 | 0.25-128 | 84.7 |
| E. coli (43 isolates) | ||||
| Ampicillin | >32 | >32 | >32->32 | 0 |
| Amoxicillin-clavulanate (2:1) | 16b | >32b | 2->32b | 46.5 |
| Piperacillin-tazobactam (4 μg/ml) | 1b | 128b | 0.5->128b | 72.1 |
| Ceftriaxone | 64 | >64 | 0.06->64 | 16.3 |
| Ceftazidime | 8 | >32 | 0.25->32 | 58.1 |
| Cefepime | 8 | >32 | 0.5->32 | 60.5 |
| Imipenem | 0.5 | 2 | 0.25-8 | 97.7 |
| Ciprofloxacin | 0.5 | >32 | 0.03->32 | 53.5 |
| Levofloxacin | 0.5 | >8 | 0.03->8 | 51.2 |
| Amikacin | 2 | 16 | 0.5->64 | 90.7 |
| Minocycline | 2 | 8 | 0.5-16 | 76.7 |
| Colistin | 0.5 | 0.5 | 0.12-128 | 97.7 |
| A. baumannii (100 isolates) | ||||
| Ampicillin-sulbactam (2:1) | 16b | 256b | 4->256b | 25 |
| Piperacillin-tazobactam (4 μg/ml) | >128b | >128b | 16->128b | 1 |
| Ceftriaxone | >64 | >64 | 8->64 | 3 |
| Ceftazidime | >32 | >32 | 8->32 | 1 |
| Cefepime | >32 | >32 | 4->32 | 1 |
| Imipenem | 16 | >16 | 1->16 | 6 |
| Levofloxacin | 8 | >8 | 2->8 | 1 |
| Amikacin | >64 | >64 | 8->64 | 4 |
| Minocycline | 1 | 1 | 0.5-4 | 100 |
| Colistin | 0.5 | 1 | 0.25->1024 | 97 |
| MRSA (91 isolates) | ||||
| Levofloxacin | 4 | 8 | ≤0.06-16 | 30.8 |
| Vancomycin | 1 | 1 | 0.5-2 | 100 |
| Minocycline | 4 | 4 | ≤0.25-8 | 96.7 |
| Linezolid | 2 | 2 | 1-4 | 100 |
| E. faecium VRc (60 isolates) | ||||
| Penicillin | >8 | >8 | >8->8 | 0 |
| Ampicillin | >16 | >16 | >16->16 | 0 |
| Piperacillin-tazobactam (4 μg/ml) | >16b | >16b | >16->16b | NAd |
| Imipenem | >16 | >16 | >16->16 | NA |
| Levofloxacin | 32 | >32 | 4->32 | 0 |
| Vancomycin | >32 | >32 | >32->32 | 0 |
| Minocycline | ≤0.25 | 2 | ≤0.25->8 | 91.7 |
| Linezolid | 2 | 2 | 1->8 | 91.7 |
| Quinupristin-dalfopristin | 0.5 | 0.5 | 0.25-2 | 96.7 |
Susceptibility breakpoints (μg/ml) used were as follows: penicillin, ≤8; ampicillin, ≤8; amoxicillin-clavulanate, ≤8; ampicillin-sulbactam, ≤8; piperacillin-tazobactam, ≤16; ceftriaxone, ≤8; ceftazidime, ≤8; cefepime, ≤8; imipenem, ≤4; levofloxacin, ≤1 for Staphylococcus spp., ≤2 for all other organisms; amikacin, ≤16; ciprofloxacin, ≤1; minocycline, ≤4; vancomycin, ≤4; colistin, ≤2; linezolid, ≤2 for Enterococcus spp., ≤4 for Staphylococcus spp.; and quinupristin-dalfopristin, ≤1. (For amoxicillin-clavulanate, ampicillin-sulbactam, and piperacillin-tazobactam, the concentration refers to the β-lactam component of the combination.)
Concentration refers to the β-lactam component of the combination.
VR, vancomycin resistant.
NA, not available; susceptibility breakpoint for Enterococcus spp. in CLSI guidelines (3).