Table 2. Three isolates selected for time-kill assay and their combination results at 24 h.

Isolates, antimicrobials + concentrations (µg)	Effects of antibiotic combination, log change = (logCFU24 − logCFU0)
	CREC4	CREC5	CREC7
T0.25 + P0.25	2.1	0.5	−0.2*
T0.25 + P1	−0.8*	−1.9*	−0.3*
T0.25 + A8	1.4	2.5	4.5
T0.25 + A16	−2*	0.5	4.3
T0.25 + M4	2	2	3.5
T0.25 + M16	1.9	1.9	3.2
T0.25 + L6.8	2.5	1	3.5
T1 + P0.25	−1.2*	−2.2*	−0.8*
T1 + P1	−1.5*	−5.5*	−1*
T1 + A8	−5.5*	−0.9*	4.2
T1 + A16	−5.5*	−1.2*	4.1
T1 + M4	−0.2*	2	3
T1 + M16	−2.2*	1.5	2.5
T1 + L6.8	2.5	1	3.3
P0.25 + A8	0.3*	−1.7*	4.5
P0.25 + A16	−5.5*	−5.5*	4.3
P0.25 + M4	2.4	1	3.5
P0.25 + M16	1.5	0.5	3.1
P0.25 + L6.8	1.5	−1.9	1.8
P1 + A8	no	−5.5*	4.1
P1 + A16	no	no	3.5
P1 + M4	2.3	−0.5	2.5
P1 + M16	1.5	−0.7	2.5
P1 + L6.8	1	−2	−2.5*

*, indicates a synergistic combination. PMB or TGC (0.25 and 1 µg/mL); MEM (4 and 16 µg/mL); and AMK (8 and 16 µg/mL) and LEV 6.8 µg/mL. No: since the low concentration can play a bactericidal effect, there is no synergistic killing experiment at this concentration. CREC, carbapenem-resistant Enterobacter cloacae; PMB, polymyxin B; TGC, tigecycline; MEM, meropenem; AMK, amikacin; LEV, levofloxacin.