In vitro Antimicrobial Activity of Ampicillin-Ceftriaxone and Ampicillin-Ertapenem Combinations Against Clinical Isolates of Enterococcus faecalis with High Levels of Aminoglycoside Resistance

Table 4.: Results of Time;Killing Experiments with Five Isolates Enterococcus faecalis Highly Resistant to Aminoglycosides: Change in log₁₀ CFU/ml from Initial Inoculum (2-5X10⁵ CFU/ml)

Antimicrobials (mg/l)	Enterococcus faecalis Strains
	2557		2648		2927		2929		2980
	4 h	24 h	4h	24h	4h	24h	4h	24h	4h	24h
None	+1.2	+3.4	+1.2	+3	+2.5	+2.8	+0.6	+3	+2.5	+3.2

A(0.5)	+0.8	+2.5	+1.4	+2.3	+2.4	+2.6	+0.3	+1.8	+0.3	+3
A(1)	+0.8	+2.2	+1.4	+2.3	+2.1	+2.6	0	+1.1	-0.4	+1.9
A(2)	+0.6	+1.5	+0.5	+1.3	+0.7	+0.4	-0.9	-2.5	-0.7	+1.5
A(4)	-0.3	-0.2	-0.9	-1	-2	-0.3	-1.9	-3.5	-1.8	-2.4

C(10)	+1.2	+3.7	+0.8	+2.9	+1.1	+3	+0.5	+2.2	-0.2	+2.6

A(0.5)+C(10)	+1	+2.3	+1.5	+2.1	+0.6	+0.4	-0.9	-0.7	-1.7	+2.6
A(1)+C(10)	+0.8	+1.9	+1.5	+1.7	-0.9	+1.4	-1.2	-3.4	-2.5	+2.4
A(2)+C(10)	+0.7	0	+0.1	+1.1	-2.9	-1.6	-1.6	-3	-2.9	-4
A(4)+C(10)	-0.5	-0.6	-0.6	-0,9	-2.7	-3.7	-2.2	-3.8	-2.9	-3.4

A(2)+C(20)	-0.5	+1.4	+0.6	+2	-2	-2.1	-1.2	-3.6	-2.3	-3
A(2)+C(40)	-0.5	+1.2	+0.6	+1.5	-2	-2.3	-2	-3.7	-2.2	-3.1
A(2)+C(80)	-0.8	+2	+0.6	+2.2	-2	-3	-1	-4	-3.3	-3.5

E(2)	+0.9	+2.6	+1.8	+2.2	+2.1	+2.7	+0.2	+2.2	+1.8	+2.9

A(0.5)+E(2)	+0.6	+1.8	+1.7	+1.9	+1.9	+2.4	-0.5	+1.8	+2.1	+2.6
A(1)+E(2)	+0.3	+1.2	+1.4	+1.6	+1.4	+1.4	-0.9	-0.9	+1.8	+3
A(2)+E(2)	-0.2	+0.4	+0.9	+0.5	-0.6	+0.9	-1.2	-3	-1.8	+2.4
A(4)+E(2)	-0.8	+0.1	-0.7	-0.7	-2	-0.4	-1.2	-3	-2.2	-2.9

A, ampicillin; C, ceftriaxone; E, ertapenem.Numbers in parenthesis are mg/l.Values are change in log₁₀ CFU/ml from initial inoculum.In bold concentrations showing bactericidal activity (decrease ≥3 log₁₀).