Table 1.
Susceptibility breakpoints of polymyxins for major pathogens.
| Organism | Profile | ||
|---|---|---|---|
| Susceptible | Intermediate | Resistant | |
| CLSI recommendations [18] | |||
| P. aeruginosa∗ | MIC ≤ 2 mg/L | MIC = 4 | MIC ≥ 8 mg/L |
| Acinetobacter spp.∗ | MIC ≤ 2 mg/L | — | MIC ≥ 4 mg/L |
| Non-Enterobacteriaceae∗ | MIC ≤ 2 mg/L | MIC = 4 | MIC ≥ 8 mg/L |
| BSAC Recommendations [19] | |||
| Pseudomonas spp.# | MIC ≤ 4 mg/L | — | MIC ≥ 8 mg/L |
| Enterobacteriaceae spp.# | MIC ≤ 4 mg/L | — | MIC ≥ 8 mg/L |
∗For colistin and polymyxin B; #for colistin only. MIC: minimum inhibitory concentration; CLSI: Clinical and Laboratory Standards Institute; BSAC: British Society for Antimicrobial Chemotherapy.