Table 1.
Antibiotic susceptibility against three colistin-heteroresistant K. pneumoniae isolates and their resistant populations.
| Antibiotics | MIC (mg/L) a, b | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| S1703-35 | S1703-109 | S1703-112 | |||||||
| P | RP1 | RP2 | P | RP1 | RP2 | P | RP1 | RP2 | |
| Colistin | 1 (S) | 128 (R) | 64 (R) | 0.25 (S) | 64 (R) | 64 (R) | 1 (S) | 256 (R) | 128 (R) |
| Polymyxin B | 1 (S) | 64 (R) | 32 (R) | 0.25 (S) | 64 (R) | 32 (R) | 1 (S) | 64 (R) | 64 (R) |
| Meropenem | 0.06 (S) | 0.125 (S) | 0.125 (S) | 0.06 (S) | 0.06 (S) | 0.06 (S) | 4 (R) | 4 (R) | 2 (I) |
| Imipenem | 1 (S) | 1 (S) | 0.5 (S) | 0.25 (S) | 0.25 (S) | 0.25 (S) | 2 (I) | 1 (S) | 1 (S) |
| Cefotaxime | 0.125 (S) | 0.25 (S) | 0.25 (S) | 0.25 (S) | 0.25 (S) | 0.125 (S) | >128 (R) | >128 (R) | >128 (R) |
| Ceftazidime | 0.5 (S) | 1 (S) | 1 (S) | 1 (S) | 1 (S) | 1 (S) | >64 (R) | >64 (R) | >64 (R) |
| Cefepime | 0.25 (S) | 1 (S) | 1 (S) | 0.125 (S) | 1 (S) | 1 (S) | >64 (R) | >64 (R) | >64 (R) |
| Amikacin | 4 (S) | 4 (S) | 4 (S) | 2 (S) | 2 (S) | 2 (S) | 32 (I) | 32 (I) | 32 (I) |
| Gentamicin | 1 (S) | 1 (S) | 1 (S) | 0.5 (S) | 0.5 (S) | 0.5 (S) | 2 (S) | 2 (S) | 1 (S) |
| Ciprofloxacin | 0.25 (S) | 0.25 (S) | 0.25 (S) | 0.06 (S) | 0.06 (S) | 0.06 (S) | >64 (R) | >64 (R) | >64 (R) |
| Aztreonam | 0.125 (S) | 0.125 (S) | 0.125 (S) | 0.125 (S) | 0.125 (S) | 0.125 (S) | >64 (R) | >64 (R) | >64 (R) |
| Tigecycline | 2 (S) | 1 (S) | 1 (S) | 2 (S) | 0.5 (S) | 0.5 (S) | 1 (S) | 1 (S) | 1 (S) |
| Piperacillin–tazobactam | 16/4 (S) | 8/4 (S) | 8/4 (S) | 8/4 (S) | 8/4 (S) | 8/4 (S) | >256/4 (R) | >256/4 (R) | >256/4 (R) |
a MIC, minimal inhibitory concentration; P, parental; RP, resistant population; S, susceptible; I, intermediate; R, resistant. b Data are underlined when the MIC increased more than 2-fold in the RP compared with the parental isolate (P).