TABLE 4.

Time-kill kinetics for antibiotic–bacterial strain combinations showing synergy^a in checkerboard testing

Antibiotic-strain combination	Phenotypeb	Strain no.	FIC index for amikacin-fosfomycin (5:2) plus comparator agentc	Time-kill kinetics result
				Log10 reduction in CFU/ml at 24 hd	Interpretive category
For Gram-negative bacteria
Aztreonam
E. cloacae	AmpC	5686	0.5	1.7	Indifference
P. aeruginosa	Wild type	ATCC 27853	0.5	2.1	Synergy
Cefepime
E. cloacae	AmpC	5686	0.375	<0.5	Indifference
E. coli	Wild type	ATCC 25922	0.5	>8	Synergy
Gentamicin–Acinetobacter sp.	MDR	8133	0.5	0.2 increase	Indifference
Meropenem
Acinetobacter sp.	MDR	1986	0.5	0.8	Indifference
E. cloacae	AmpC	5686	0.5	1.3	Indifference
K. pneumoniae	KPC	25	0.375	ND
For Gram-positive bacteria
Azithromycin–S. aureus	MSSA	ATCC 29213	0.5	3.0	Synergy
Daptomycin–E. faecalis	Wild type	ATCC 29212	0.5	2.7	Synergy

^aDefined as a FIC index of ≤0.5.

^bAmpC, AmpC type β-lactamase; KPC, Klebsiella pneumoniae carbapenemase; MDR, multidrug resistant.

^cDetermined by checkerboard synergy testing.

^dND, not determined.