TABLE 2.

Amino acid differences between CTX-M-12 β-lactamase and the related cefotaxime-hydrolyzing enzymes CTX-M-1 (MEN-1) and CTX-M-3

β-Lactamase	Amino acid residue at position:
	12	77	89	114	140	278	288
CTX-M-1	Thr	Val	Asn	Asp	Ser	Val	Asn
CTX-M-3	Thr	Ala	Asn	Asn	Ala	Val	Asp
CTX-M-12	Ala	Ala	Ser	Asn	Ala	Ile	Asp