TABLE 1.

Characteristics of bacterial strains investigated, including resistance determinants (10, 20), MICs of TGC and COL, FICIs and SBPIs for TGC/COL combinations, and results from time-kill assays

Strain	Feature(s)	TGC MIC (μg/ml)	COL MIC (μg/ml)	FICIa	SBPI	Time-kill assay resultsa
E. coli NCTC 12241	Antibiotic-susceptible type strain	0.064	0.75	0.625 (I)	40
E. coli EC5	ST131 CTX-M-15 producer	0.064	1	0.5 (S)	39.95	S
E. coli EC204	Carbapenem-resistant NDM-1 producer	0.25	0.38	0.374 (S)	24.13	S
E. coli EC421	Carbapenem-resistant NDM-1 producer	0.16	8	0.748 (I)	20.13
E. coli EC405	Carbapenem-resistant NDM-5 producer	0.16	0.75	1 (I)	10
E. aerogenes NCTC 9753	Antibiotic-susceptible type strain	0.16	0.75	0.56 (I)	40
E. aerogenes EA2	Carbapenem-susceptible CTX-M-1 producer	0.25	3	0.188 (S)	39.95	S
E. aerogenes EA1	Carbapenem -resistant (porin loss, AmpC hyperproducer); in vivo derivative of EA2	0.125	0.38	0.75 (I)	24.13
E. cloacae NCTC 13380	Antibiotic-susceptible type strain	0.16	0.5	0.56 (I)	39
E. cloacae TGC-R	TGC-resistant efflux mutant	8	1.5	0.5 (S)	8.5	S
K. pneumoniae NCTC 9633	Antibiotic-susceptible type strain	0.125	0.38	0.125 (S)	12	I
K. pneumoniae KP52	Carbapenem-resistant OXA-48 producer	0.5	1	0.375 (S)	12	S
K. pneumoniae KPC-3	Carbapenem-resistant KPC-3 producer	1	0.5	0.75 (I)	9
K. pneumoniae KP51	Carbapenem-susceptible CTX-M-15 producer	4	0.5	0.313 (S)	9	S
K. pneumoniae KP96	Carbapenem-resistant VIM-1 and KPC-2 producer	0.5	0.38	0.531 (I)	39.95
S. marcescens NCTC 13382	Antibiotic-susceptible type strain	0.125	>256	9 (A)	0.125
S. marcescens	Carbapenem-resistant NDM-1 producer	1.5	>256	9 (A)	0.09
S. marcescens SM346	TGC-resistant efflux mutant	6	2	5 (A)	0.125

^aS, synergy; I, intermediate or additive; A, antagonism.