TABLE 1.

β-Lactamase classes detected by PCR grouped by results of ESBL confirmation test on screening-positive strains^a

β-Lactamase class(es) detected	Nonconfirmed ESBL test				Confirmed ESBL test
	E. coli		K. pneumoniae		E. coli		K. pneumoniae
	n	%	n	%	n	%	n	%
AmpC only	3	5.8	9	17.6
TEM only	11	21.2			7	10.4
SHV only	1	1.9	5	9.8	4	6.0	17	25.0
CTX-M only	1	1.9			9	13.4	6	8.8
TEM+SHV	3	5.8			13	19.4	16	23.5
TEM+CTX-M					24	35.8
SHV+CTX-M							9	13.2
AmpC+TEM	26	50.0	1	2.0
AmpC+SHV	1	1.9	19	37.3	1	1.5	6	8.8
TEM+SHV+CTX			3	5.9	1	1.5		13.2
AmpC+TEM+SHV	2	3.8	9	17.6	3	4.5
AmpC+TEM+CTX					2	3.0	1	1.5
AmpC+SHV+CTX-M					1	1.5	1	1.5
AmpC+TEM+SHV+CTX-M
PCR negative	4	7.7	5	9.8	2	3.0	3	4.4
Totals	52		51		68		67
Any AmpC	32	61.5	38	74.5	7	10.4	8	11.8
Any TEM	42	80.8	13	25.5	50	74.6	26	38.2
Any SHV	7	13.5	17	33.3	23	34.3	58	85.3
Any CTX-M	1	1.9	3	5.9	36	55.2	26	38.2

^an, Number of isolates.