. 2018 Nov 14;74(3):582–593. doi: 10.1093/jac/dky458

Table 1.

MICs of several antibiotic classes for day 20 replicates compared with the initial isolate

Strain^a	MIC (mg/L)^b
Strain^a	CST	PMB	OctC4	AMX	ATM	FEP	CRO	CHL	CIP	GEN	MEM	PIP	TET	TGC	TMP
Initial	≤0.25^S	≤0.125^S	8	>64^R	>64^R	≥16^R	>64^R	≥32^R	>64^R	≤4^S	≥32^R	>64^I	>64^R	≤2^S,I	>64^R
CST_1	>128^R	>128^R	≤8	>64^R	>64^R	≥16^R	>64^R	≤8^S	≥32^R	4^S	≥32^R	>64^I	>64^R	≤4^S,R	>64^R
CST_2	>128^R	>128^R	≤4	>64^R	>64^R	>64^R	>64^R	4^S	≥32^R	≤4^S	≥32^R	>64^I	>64^R	2^I	>64^R
CST_3	≥128^R	≥128^R	≤4	>64^R	>64^R	>64^R	>64^R	8^S	>64^R	≤4^S	>64^R	>64^I	>64^R	≤4^I,R	>64^R
CST_4	>128^R	>128^R	≤8	>64^R	>64^R	>64^R	>64^R	≤8^S	>64^R	≤4^S	>64^R	>64^I	>64^R	≤4^I,R	>64^R
CST_5	>128^R	>128^R	2	>64^R	>64^R	>64^R	>64^R	≤8^S	>64^R	≤4^S	>64^R	>64^I	>64^R	≤4^I,R	>64^R
CST_6	>128^R	>128^R	≤8	>64^R	>64^R	>64^R	>64^R	8^S	>64^R	≤4^S	>64^R	>64^I	>64^R	≥4^R	>64^R
PMB_1	128^R	128^R	≤4	>64^R	>64^R	>64^R	32^R	4^S	32^R	≤4^S	>64^R	>64^I	>64^R	≤4^I,R	>64^R
PMB_2	>128^R	>128^R	8	>64^R	>64^R	≤8^I	>64^R	4^S	>64^R	≤4^S	≤0.25^S	>64^I	>64^R	≤2^S,I	>64^R
PMB_3	>128^R	>128^R	4	>64^R	>64^R	≥32^R	>64^R	8^S	>64^R	2^S	≥32^R	>64^I	>64^R	2^I	>64^R
PMB_4	>128^R	>128^R	4	>64^R	>64^R	≥8^I,R	≥32^R	≤2^S	48^R	2^S	≥8^R	>64^I	>64^R	2^I	>64^R
PMB_5	>128^R	>128^R	≤8	>64^R	>64^R	≥8^I,R	≥32^R	≤8^S	>64^R	≤4^S	≥2^I,R	>64^I	>64^R	≤2^S,I	>64^R
PMB_6	>128^R	>128^R	≤8	>64^R	>64^R	≥16^R	>64^R	8^S	>64^R	≤4^S	≥32^R	>64^I	>64^R	≤4^I,R	>64^R
OctC4_1	0.25^S	≤0.25^S	32	>64^R	>64^R	≥16^R	>64^R	8^S	>64^R	≤2^S	≥32^R	>64^I	>64^R	≤2^S,I	>64^R
OctC4_2	0.25^S	0.25^S	32	>64^R	>64^R	≥8^I,R	>64^R	8^S	>64^R	≤2^S	≥32^R	>64^I	≤2^S	≤1^S	≥8^R
OctC4_3	≤0.5^S	0.25^S	32	>64^R	>64^R	≤4^S,I	32^R	8^S	>64^R	≤4^S	≤0.25^S	>64^I	>64^R	2^I	>64^R
OctC4_4	≤0.5^S	0.25^S	>32	>64^R	>64^R	≤4^S,I	32^R	8^S	>64^R	1^S	≤0.25^S	>64^I	≥2^S,R	≤2^S,I	≥4^R
OctC4_5	0.5^S	0.5^S	32	>64^R	>64^R	>64^R	>64^R	≤8^S	>64^R	2^S	>64^R	>64^I	>64^R	2^I	>64^R
OctC4_6	≤0.5^S	≤0.5^S	32	>64^R	>64^R	≤4^S,I	≥32^R	≤16^{S, I}	>64^R	2^S	≤0.25^S	>64^I	>64^R	2^I	>64^R

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.