Table 1.

MICs of imipenem, meropenem, and doripenem and fractional inhibitory concentration indexes (FICi) of dual carbapenem combinations for the eleven carbapenemase-producing Pseudomonas aeruginosa clinical strains.

P. aeruginosa	ST	Carbapenemases	MIC (mg/L)			ΣFICi (mg/L)
			IMP	MEM	DOR	IMP + MEM	IMP + DOR	MEM + DOR
ARA01-015	235	VIM-2	128	16	64	1.06	0.56	1.00
ARA01-045	973	VIM-2	64	32	32	0.75	1.06	0.63
CAT05-004	253	VIM-1	128	128	128	1.00	0.50	0.50
CLE02-006	664	IMP-1	128	64	64	0.75	1.00	0.75
CVA03-019	175	OXA-2/VIM-20	128	32	32	0.75	0.75	0.75
MAD02-005	175	GES-5	64	128	64	0.75	0.75	0.63
MAD02-007	175	VIM-2	128	32	32	0.50	1.25	1.00
MAD02-021	235	GES-5	64	128	64	0.63	0.75	0.63
MAD04-041	155	IMP-8	128	16	16	0.75	1.50	0.63
MAD05-041	111	VIM-2	128	16	16	1.00	0.75	0.50
MUR01-018	111	IMP-33	256	128	128	1.06	1	0.25

ST: Sequence Type. According to EUCAST guidelines: IMP (imipenem) R > 4 mg/L; MEM (meropenem) R > 8 mg/L; DOR (doripenem) R > 4 mg/L. Data on STs and carbapenemases were obtained from a previous study, which includes the complete description of the resistome of the studied strains [23]. Synergistic activity is highlighted in bold. FICi ≤ 0.5 indicates synergy; FICi = 0.5–4 indicates no interaction; and FICi > 4 indicates antagonism.