TABLE 2.

Results of checkerboard synergy testing among CR-Kp strains

K. pneumoniae strain no.	MIC (μg/ml)a					FICb
	AMK	COL	DOR	TGC	TMP-SMX	AMK-COL	AMK-DOR	AMK-TGC	AMK–TMP-SMX
615	4	>64	128	1	>128	1	0.75	2	0.25
383	16	0.125	8	2	>128	0.75	0.5	0.75	0.375
871	16	0.125	16	2	>128	1	0.625	0.75	0.375
930	16	0.25	32	1	0.125	1	0.375	0.75	2
1	16	>64	64	0.25	>128	0.265	0.5156	0.75	0.25
136	16	>64	64	2	16	0.375	0.5	0.75	0.5
294	16	0.5	4	0.25	>128	0.75	0.5	0.75	0.25
584	16	64	>128	2	128	0.375	0.5156	2	0.5
928	16	32	4	1	>128	0.375	0.25	1	0.3125
184	32	16	64	0.25	>128	0.75	1	2	0.375
216	32	16	4	0.25	>128	0.5	0.75	0.5625	0.25
484	32	0.5	>128	2	>128	0.75	0.5	0.5625	0.5
539	32	0.25	64	0.5	>128	1.5	1	2	0.3125
587	32	0.25	64	0.5	>128	0.75	1	2	0.375
669	32	0.25	128	2	1	1	0.5	0.75	0.56
705	32	0.125	128	0.5	>128	0.675	0.75	1	0.375
709	32	0.125	16	2	>128	1	0.5625	0.75	0.375
94	32	64	128	2	>128	0.5	1	0.5625	0.3125
649	32	64	>128	1	>128	0.625	0.75	0.625	0.375
692	32	0.25	8	2	>128	2	0.75	0.75	0.3125

^aAMK, amikacin; COL, colistin; DOR, doripenem; TGC, tigecycline; TMP-SMX, trimethoprim-sulfamethoxazole.

^bThe following concentrations were tested for each agent: AMK, 2 to 128 μg/ml; COL, 0.06 to 64 μg/ml; DOR, 0.125 to 128 μg/ml; TGC, 0.06 to 64 μg/ml; TMP-SMX, 0.125 to 128 μg/ml. TMP and SMX were tested at a fixed ratio of 1:19 in accordance with CLSI susceptibility testing guidelines (10). The percentages of synergy (FIC of ≤0.5) were as follows: AMK-COL, 30%; AMK-DOR, 35%; AMK-TGC, 0%; and AMK–TMP-SMX, 90%.