. 2007 Mar 26;51(6):1987–1994. doi: 10.1128/AAC.01509-06

TABLE 2.

Antimicrobial susceptibility test results for 186 bloodstream isolates of ESBL-producing E. coli, K. pneumoniae, and P. mirabilis

Antimicrobial agent	E. coli (n = 104)			K. pneumoniae (n = 58)			P. mirabilis (n = 24)
	MIC (μg/ml)^a		No. (%) susceptible^b	MIC (μg/ml)		No. (%) susceptible	MIC (μg/ml)		No. (%) susceptible
	MIC₅₀	MIC₉₀	No. (%) susceptible^b	MIC₅₀	MIC₉₀	No. (%) susceptible	MIC₅₀	MIC₉₀	No. (%) susceptible
Amikacin	2	8	102 (98.1)	2	16	53 (91.4)	2	4	24 (100)
Amoxicillin-clavulanic acid	16/8	128/64	48 (46.1)	8/4	128/64	32 (55.1)	2/1	4/2	24 (100)
Aztreonam	256	256	0 (0)	256	256	0 (0)	0.25	1	0 (0)
Cefoxitin	2	≥64	74 (71.1)	2	≥64	43 (74.1)	2	8	100 (0)
Cefepime	16	256	0 (0)	1	256	0 (0)	2	32	0 (0)
Cefotaxime	256	256	0 (0)	8	256	0 (0)	16	256	0 (0)
Ceftazidime	256	256	0 (0)	256	256	0 (0)	4	16	0 (0)
Ciprofloxacin	≥16	≥16	9 (8.6)	2	≥16	27 (46.5)	≥16	≥16	3 (12.5)
Gentamicin	0.5	≥32	59 (56.7)	0.25	≥32	40 (68.9)	≥32	≥32	0 (0)
Imipenem	0.25	0.25	104 (100)	0.25	0.25	58 (100)	1	4	24 (100)
Levofloxacin	≥32	≥32	9 (8.6)	2	≥32	28 (48.2)	≥32	≥32	3 (12.5)
Meropenem	0.03	0.25	104 (100)	0.03	0.25	58 (100)	0.03	0.25	24 (100)
Piperacillin-tazobactam	2/4	256/4	86 (82.7)	2/4	256/4	37 (63.8)	0.5/4	1/4	24 (100)
Trimethoprim-sulfamethoxazole	≥4/76	≥4/76	35 (33.6)	0.12/2.38	≥4/76	2 (55.2)	0.12/2.38	≥4/76	14 (58.3)

MIC₅₀ and MIC₉₀ are the MICs at which 50 and 90% of isolates, respectively, are inhibited.

In accordance with CLSI guidelines, all ESBL-producing isolates were considered resistant to all penicillins, cephalosporins, and aztreonam regardless of the MICs that emerged for these drugs during in vitro susceptibility testing (see reference 9).