TABLE 3.

Increasing numbers of β-lactamases in well-characterized families^a

Enzyme type	Class	Functional group	No. in class by yr
			1961	1995	2000	2005	2010	2015	2018
CMY	C	1	0	1	6	22	64	136	139
PDCb	C	1	0	(1)	(1)	(1)	10	30	226
ADCc	C	1	0	0	(1)	7	7	7	81
All TEMs	A	2b, 2be, 2br	0	36	86	153	178	219	224
All SHVs	A	2b, 2be, 2br	0	6	26	89	134	182	193
CTX-M	A	2be	0	2	9	51	103	172	182
KPC	A	2f	0	0	0	3	11	22	24
All OXAs	D	2d	0	18	28	88	202	498	520
IMP	B	3	0	1	3	23	29	48	53
VIM	B	3	0	0	2	12	27	41	46
NDM	B	3	0	0	0	0	1	12	14
Estimated total of all unique β-lactamases			(<13)d	217	309	584	1,003	1,855	2,771

^aSome data are from reference 224, as well as from http://www.lahey.org/Studies/ and https://www.ncbi.nlm.nih.gov/bioproject/PRJNA313047.

^bPDC, Pseudomonas-derived cephalosporinase family, first named in 2009 (136). AmpC pseudomonal cephalosporinases were described as early as 1965 (137). This family was not included in the Lahey database http://www.lahey.org/Studies/.

^cADC, Acinetobacter-derived cephalosporinase, family first named in 2005 (190). The name ADC-1 was assigned to an enzyme first described in 2000 (135). This family was not included in the Lahey database http://www.lahey.org/Studies/.

^dEstimated, based on data from references 18 and 92 that most likely included some of the same enzymes.