Table 1.
Straina | MIC (mg/L)b |
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CST | PMB | OctC4 | AMX | ATM | FEP | CRO | CHL | CIP | GEN | MEM | PIP | TET | TGC | TMP | |
Initial | ≤0.25S | ≤0.125S | 8 | >64R | >64R | ≥16R | >64R | ≥32R | >64R | ≤4S | ≥32R | >64I | >64R | ≤2S,I | >64R |
CST_1 | >128R | >128R | ≤8 | >64R | >64R | ≥16R | >64R | ≤8S | ≥32R | 4S | ≥32R | >64I | >64R | ≤4S,R | >64R |
CST_2 | >128R | >128R | ≤4 | >64R | >64R | >64R | >64R | 4S | ≥32R | ≤4S | ≥32R | >64I | >64R | 2I | >64R |
CST_3 | ≥128R | ≥128R | ≤4 | >64R | >64R | >64R | >64R | 8S | >64R | ≤4S | >64R | >64I | >64R | ≤4I,R | >64R |
CST_4 | >128R | >128R | ≤8 | >64R | >64R | >64R | >64R | ≤8S | >64R | ≤4S | >64R | >64I | >64R | ≤4I,R | >64R |
CST_5 | >128R | >128R | 2 | >64R | >64R | >64R | >64R | ≤8S | >64R | ≤4S | >64R | >64I | >64R | ≤4I,R | >64R |
CST_6 | >128R | >128R | ≤8 | >64R | >64R | >64R | >64R | 8S | >64R | ≤4S | >64R | >64I | >64R | ≥4R | >64R |
PMB_1 | 128R | 128R | ≤4 | >64R | >64R | >64R | 32R | 4S | 32R | ≤4S | >64R | >64I | >64R | ≤4I,R | >64R |
PMB_2 | >128R | >128R | 8 | >64R | >64R | ≤8I | >64R | 4S | >64R | ≤4S | ≤0.25S | >64I | >64R | ≤2S,I | >64R |
PMB_3 | >128R | >128R | 4 | >64R | >64R | ≥32R | >64R | 8S | >64R | 2S | ≥32R | >64I | >64R | 2I | >64R |
PMB_4 | >128R | >128R | 4 | >64R | >64R | ≥8I,R | ≥32R | ≤2S | 48R | 2S | ≥8R | >64I | >64R | 2I | >64R |
PMB_5 | >128R | >128R | ≤8 | >64R | >64R | ≥8I,R | ≥32R | ≤8S | >64R | ≤4S | ≥2I,R | >64I | >64R | ≤2S,I | >64R |
PMB_6 | >128R | >128R | ≤8 | >64R | >64R | ≥16R | >64R | 8S | >64R | ≤4S | ≥32R | >64I | >64R | ≤4I,R | >64R |
OctC4_1 | 0.25S | ≤0.25S | 32 | >64R | >64R | ≥16R | >64R | 8S | >64R | ≤2S | ≥32R | >64I | >64R | ≤2S,I | >64R |
OctC4_2 | 0.25S | 0.25S | 32 | >64R | >64R | ≥8I,R | >64R | 8S | >64R | ≤2S | ≥32R | >64I | ≤2S | ≤1S | ≥8R |
OctC4_3 | ≤0.5S | 0.25S | 32 | >64R | >64R | ≤4S,I | 32R | 8S | >64R | ≤4S | ≤0.25S | >64I | >64R | 2I | >64R |
OctC4_4 | ≤0.5S | 0.25S | >32 | >64R | >64R | ≤4S,I | 32R | 8S | >64R | 1S | ≤0.25S | >64I | ≥2S,R | ≤2S,I | ≥4R |
OctC4_5 | 0.5S | 0.5S | 32 | >64R | >64R | >64R | >64R | ≤8S | >64R | 2S | >64R | >64I | >64R | 2I | >64R |
OctC4_6 | ≤0.5S | ≤0.5S | 32 | >64R | >64R | ≤4S,I | ≥32R | ≤16S, I | >64R | 2S | ≤0.25S | >64I | >64R | 2I | >64R |
Resistance determined as per CLSI guidelines, except EUCAST guideline used for tigecycline (S, susceptible; I, intermediate; R, resistant). Fluctuations in MIC values (n = 4) are displayed by two letters defining the resistance level. Grey shading indicates resistant MIC values. Resistance to octapeptin C4 defined at an MIC ≥32 mg/L, as no clinical breakpoint has been reported for this compound.
The initial polymyxin-susceptible isolate (20_GR_12) and this strain subjected to 20 days of treatment with colistin (CST), polymyxin B (PMB) or octapeptin C4 (OctC4) (_1, _2, _3, _4, _5 and _6 indicate replicate numbers).
MIC determined for: CST, colistin; PMB, polymyxin B; OctC4, octapeptin C4; AMX, amoxicillin; ATM, aztreonam; FEP, cefepime; CRO, ceftriaxone; CHL, chloramphenicol; CIP, ciprofloxacin; GEN, gentamicin; MEM, meropenem; PIP, piperacillin; TET, tetracycline; TGC, tigecycline; and TMP, trimethoprim.