TABLE 1.

MICs of CTX-M-64 mutants toward different β-lactams^a

Enzyme/mutant	MIC (μg/ml) for:
	AMP	CEP	CFX	CRO	CTX	CAZ
CTX-M-64 WT	≥2,048	1,024	2,048	1,024	2,048	32
Vector control	2	2	0.5	<0.25	<0.25	0.03
I58V	2,048	512	1,024	512	512	4
G240D	≥2,048	512	1,024	1,024	512	2
G240L	≥2,048	512	2,048	1,024	256	2
G240A	≥2,048	512	1,024	1,024	512	4
G240E	≥2,048	512	1,024	512	256	2
G240R	≥2,048	512	1,024	512	128	0.25
G240D, I58V	≥2,048	512	2,048	1,024	512	2
G240D, K254Q, D255G	≥2,048	512	2,048	1,024	512	2
G240D, I58V, K254Q, D255G	≥2,048	1,024	2,048	1,024	512	1
I58V, K254Q, D 255G	≥2,048	512	1,024	512	512	16
G240D, P270Q, K271N	≥2,048	1,024	2,048	1,024	1,024	2
I58V, L33A	1,024	512	1,024	1,024	512	4
I58V, V52A	512	512	512	512	256	4
I58V, L287A	512	512	512	512	256	4
CTX-M-14 WT	2,048	256	1,024	512	128	1

^aAMP, ampicillin; CEP, cephalothin; CFX, cefuroxime; CRO, ceftriaxone; CTX, cefotaxime; CAZ, ceftazidime.