TABLE 1.

Median MIC and MBC values of colistin in CAMHB and ISB with different inocula.

	CAMHB 105 CFU/mL		CAMHB 106 CFU/mL		ISB 105 CFU/mL		ISB 106 CFU/mL
	MIC [mg/L]	MBC [mg/L]	MIC [mg/L]	MBC [mg/L]	MIC [mg/L]	MBC [mg/L]	MIC [mg/L]	MBC [mg/L]
Colistin-susceptible E. coli
ATCC 25922	1	1	2	2	0.5	2	2	4
UTI89	0.5	0.5	1	1	0.5	1	1	2
CHD3	0.5	0.5	1	1	1	2	4	4
CHD4	0.5	0.5	1	1	0.5	2	2	2
CHD5	0.5	0.5	1	1	0.5	2	2	2
CHD6	0.5	0.5	1	2	0.5	2	1	2
CHD7	0.25	0.5	1	1	0.25	1	1	2
CHD8	0.5	0.5	1	1	0.5	1	2	2
CHD10	1	1	2	2	0.5	4	4	4
CHD11	0.5	0.5	1	1	0.5	2	2	2
CHD12	0.5	1	1	2	0.5	2	2	2
CHD16	1	1	1	1	0.5	1	2	2
Mean (range)	0.5 (0.25–1)	0.5 (0.5–1)	1 (1–2)	1 (1–2)	0.5 (0.25–0.5)	2 (1–4)	2 (1–4)a	2 (2–4)
mcr-1-positive E. coli
Af23	8	8	8	8	16	16	8	8
Af24	8	16	16	16	32	32	16	64
Af31	6	16	8	16	16	16	16	32
Af40	8	16	8	32	16	16	16	32
Af45	8	16	8	16	32	32	16	64
Af48	6	8	8	16	16	32	16	16
Af49	8	16	8	8	32	32	16	32
CDF1	4	16	8	32	16	32	8	16
CDF2	16	16	16	32	32	32	32	32
CDF6	8	16	4	32	24	48	16	64
CDF8	8	16	8	64	16	24	16	32
S115	8	8	8	8	16	64	16	64
PS1	8	8	8	8	24	48	16	64
Median (range)	8 (4–16)	16 (8–16)	8 (8–16)	16 (8–32)	16 (8–32)	32 (8–64)	16 (8–32)	32 (8–64)

≥4 fold (± 2 log₂) difference with p < 0.0001: ^acompared to 10⁵ CFU/ml in same media.