TABLE 1.

Rest values obtained by time-kill, Etest, and checkerboard in vitro testing^a

Isolate	MIC (μg/ml)			Test resultb
				PB-RIF			PB-TGC			TGC-RIF
	PB	RIF	TGC	Time-kill	Etest	Checkerboard	Time-kill	Etest	Checkerboard	Time-kill	Etest	Checkerboard
8	1	8	8	5.5	1.2	0.6	5.5	1.8	0.5	1.2	1.0	0.4
16	1	4	4	1.0	1.4	1.0	1.0	2.3	1.1	1.6	1.7	0.8
23	1	4	8	1.0	1.2	0.6	1.0	1.8	0.6	1.2	1.0	0.5
25	1	4	4	4.4	1.5	1.0	4.4	2	1.1	1.4	2	0.8
32	1	≥32	4	3.9	0.9	1.0	2.6	1.5	1.2	0.6	0.8	0.8
41	1	8	8	1.8	1.5	0.7	1.8	2	0.8	1.2	1.5	0.8
91	2	2	4	2.3	1.5	1.0	2.3	2	1.1	5.5	1.0	1
104	2	8	4	1.0	1.2	1.0	1.0	2	0.8	1.5	1.0	0.8
128	1	4	≥32	2.2	0.9	1.0	2.9	1.5	0.3	1.1	1.0	1.6
112	1	2	4	3.6	1.5	0.5	3.6	2	1.1	5.7	1.5	1.1
8879	2	2	2	2.5	1.8	0.6	2.5	2	1.1	4	1.5	0.6
3160	2	4	≥32	1.0	1	0.5	1.0	1.7	0.6	1.3	1.5	0.6
27640	≥16	≥32	≥32	2.8	0.2	0.02	1.0	0.6	1.0	1.1	0.7	0.4
18351	≥16	2	8	4.5	0.7	0.1	1.0	5	0.3	1.2	0.9	0.4
9447	≥16	≥32	4	1.0	2	0.1	1.0	1.8	0.5	1.0	2.0	1
11171	≥16	≥32	4	1.0	1.7	0.5	1.0	1.7	0.5	1.0	2.0	16

^aAbbreviations: PB, polymyxin B; RIF, rifampin; TGC, tigecycline.

^bValues for the time-kill column demonstrate the reduction in CFU/ml expressed in log₁₀, while values for Etest and checkerboard columns represent the lowest FIC index achieved in testing. Antibiotic-test-isolate combinations demonstrating in vitro synergy are shown in bold italic text, while those demonstrating antagonism are shown in bold text.