TABLE 1.

Control strains producing well-characterized β-lactamases

Strain	Organism	β-Lactamase	Group^a	Source or reference
CF2	Enterobacter cloacae	CTX-M-1	I	18
Rio-4	Proteus mirabilis	CTX-M-2	II	5
VER-1	E. cloacae	CTX-M-3	I	18
Cfr2525/96	Citrobacter freundii	CTX-M-3	I	21
Eco3553/98	E. coli	CTX-M-15	I	1
34	Salmonella enterica serovar Typhimurium	CTX-M-5	II	9
Rio-3	Enterobacter aerogenes	CTX-M-8	III	5
785D	E. coli	CTX-M-9	IV	36
EC97/38582	E. coli	CTX-M-10	I	31
EC984167	E. coli	CTX-M-14	IV	26
CF1	E. coli	CTX-M-14	IV	18
Rio-6	E. coli	CTX-M-16	IV	4
BM4493	Klebsiella pneumoniae	CTX-M-17	IV	13
ILT-2	K. pneumoniae	CTX-M-18	IV	35
ILT-3	K. pneumoniae	CTX-M-19	IV	35
CT1^b	E. coli	Toho-1	II	25
S1^b	E. coli	SHV-2		20
S2^b	E. coli	SHV-7		8
T1^b	E. coli	TEM-3		20
T4^b	E. coli	TEM-10		20
T5^b	E. coli	TEM-50		37

↵a Group I includes CTX-M-1, -3, -10 to -12, -15 (UOE-1), -22, -23, -28, -29, and -30. Group II includes CTX-M-2, -4 to -7, and -20 and Toho-1. Group III includes CTX-M-8. Group IV includes CTX-M-9, -13, -14, -16, to -19, -21, and -27 and Toho-2. Finally, group V includes CTX-M-25 and -26. We were unable to obtain a strain producing any group V enzymes.
↵b These strains are part of an unpublished isogenic panel. The original strains producing these β-lactamases were provided to the Center for Research in Anti-Infectives and Biotechnology by the referenced authors listed in the table.