TABLE 1.

Minimum inhibitory concentration (MIC) values of commonly used clinical antibiotics and NG against 21 colistin-resistant GNB.

Species	Strains	Antibiotics	ATM	CAZ	FEP	IPM	CIP	LVX	GEN	TOB	COL	NG
		Breakpoints (S-R)	8–32	8–32	8–32	2–8	0.5–2	1–4	4–16	4–16	2–4
K. pneumoniae	FK1913	MIC (μg/ml)	≥256	≥256	≥256	32	≥256	128	≥256	≥256	>64	>512
	FK6663		≥256	≥256	≥256	32	≥256	≥256	≥256	≥256	8	>512
	FK169		≥256	≥256	≥256	32	128	32	128	64	>64	>512
	FK6556		64	64	64	16	4	8	16	16	16	>512
	FK1342		128	≥256	≥256	0.25	1	0.5	1	4	≥64	>512
	FK1986		0.0125	0.25	0.0125	0.25	0.0125	0.025	2	1	8	>512
	FK3994		≥256	128	≥256	32	≥256	64	≥256	≥256	64	>512
E. coli	DC3846	MIC (μg/mL)	128	64	≥256	0.5	≥256	128	≥256	64	8	>512
	DC7333		≥256	≥256	≥256	16	≥256	128	128	≥256	8	>512
	DC3539		64	128	≥256	0.5	64	16	128	128	8	>512
	DC3806		64	64	16	1	4	8	16	16	8	>512
	DC5286		≥256	128	≥256	0.25	128	64	4	4	8	>512
	DC90		≥256	32	64	≥256	64	32	≥256	128	4	>512
	DC3737		64	64	64	16	4	8	16	16	8	>512
A. baumannii	BM2349	MIC (μg/ml)	64	64	64	64	32	8	64	64	4	>512
	BM2431		64	64	64	16	4	8	1	1	32	>512
	BM2412		16	64	64	16	4	8	4	1	16	>512
	BM2370		8	32	128	8	128	8	4	1	8	>512
	BM2622		64	64	64	8	4	8	16	16	4	>512
	BM1539		16	8	64	16	4	2	1	1	8	>512
	BM1595		2	32	8	4	64	8	128	128	8	>512

Bold strain number indicates multidrug-resistant (MDR) strain; Bold MIC values mean resistance.

GNB, gram-negative bacteria; MIC, minimum inhibitory concentration; ATM, aztreonam; CAZ, ceftazidime; FEP, cefepime; IMP, imipenem; CIP, ciprofloxacin; LVX, levofloxacin; GEN, gentamicin; TOB, tobramycin; COL, colistin; NG, naringenin; S, susceptible; R, resistance.