TABLE 2.

Results of isoelectric focusing, β-lactamase characterization, susceptibility testing, and pulsed-field gel electrophoresis analysis

Isolate group	pI(s)	β-Lactamase(s)a	No. of isolates	Range of MICs (μg/ml)b									PFGE pattern(s) (no. of isolates)c
				AMC	FOX	CAZ	CAZ + CLA	CTX	CTX + CLA	ATM	FEP	IPM
1a	9.0, 7.6	CMY-2, NE-SHV	7	64-128	128-256	64->256	64->256	16-64	16-32	16-32	0.13-0.5	0.25-1
	9.0, 7.6, 5.4	CMY-2, NE-SHV, TEM-1	23	64-128 (64/128)	128->256 (128/>256)	64->256 (128/>256)	64->256 (128/>256)	16-64 (32/64)	8-32 (16/32)	16-64 (16/32)	0.13-0.5 (0.25/0.5)	0.25-8 (0.5/1)
1b	7.8, 7.6, 5.4	DHA-1, NE-SHV, TEM-1	12	64-128 (64/128)	128->256 (256/>256)	16-32 (16/32)	64-256 (64/256)	2-16 (4/16)	4-64 (16/64)	2-16 (4/16)	0.06-0.25 (0.13/0.25)	0.5-1 (0.5/1)	Ia (3), XI (1), XIII (1), XV (1), XV (1), XVI (1), XVIII (1)
2a	8.4, 7.8, 7.6, 5.4	CTX-M-3, DHA-1, NE-SHV, TEM-1	9	64-128	≥128	32	64-128	32-64	2-16	16-64	8-32	0.5-2	Ic (1), II (1), III (1), VIII (1), XVII (1)
	7.9, 7.8, 7.6, 5.4	CTX-M-14, DHA-1, NE-SHV, TEM-1	1	64	>256	16	32	128	16	16	32	2	VI (1)
2b	8.4, 8.2, 7.8, 7.6, 5.4	CTX-M-3, E-SHV, DHA-1, NE-SHV, TEM-1	5	64-128	≥256	≥256	64-128	32-128	4-16	≥256	8-16	0.5-2	Id (1), X (1), XIV (1)
	8.2, 7.9, 7.8, 7.6, 5.4	E-SHV, CTX-M-14, DHA-1, NE-SHV, TEM-1	1	64	256	>256	128	128	8	>256	64	1
2c	8.2, 7.8, 7.6, 5.4	E-SHV, DHA-1, NE-SHV, TEM-1	8	64-128	≥128	≥128	64-128	8-32	4-16	≥128	2-8	0.5-2	Ib (2), IV (1), V (1), VII (1), IX (1), XII (1)
	8.4, 8.25, 7.6, 5.4	CTX-M-3, CMY-8, NE-SHV, TEM-1	9	16-32	>256	16-64	8-32	64-256	16-64	8-64	2-16	0.25-1
	9.0, 8.4, 7.6, 5.4	CMY-2, CTX-M-3, NE-SHV, TEM-1	1	64	>256	256	128	256	128	256	4	2
	9.0, 8.4, 8.2, 7.6, 5.4	CMY-2, CTX-M-3, E-SHV, NE-SHV, TEM-1	1	128	>256	>256	128	>256	128	64	256	4
3	8.2, 7.6, 5.4	IMP-8, NE-SHV, TEM-1	1	64	>256	>256	256	32	32	64	8	1
	8.2, 7.6, 5.4	IMP-8, E-SHV, NE-SHV, TEM-1	1	64	>256	>256	256	32	32	0.25	4	2
4	8.2, 7.6, 5.4	E-SHV, NE-SHV, TEM-1	3	8-16	32-64	≥256	8-16	64-256	16-32	≥256	8-16	0.5-1
	8.2, 7.6	E-SHV, NE-SHV	2	16, 32	32, 64	>256	16	128, 256	8	>256	8, 16	1
	7.9, 7.6, 5.4	CTX-M-14, NE-SHV, TEM-1	1	64	32	16	8	128	8	32	8	1
	7.9, 7.6	CTX-M-14, NE-SHV	2	64	32	16, 32	8, 16	64	2, 4	8, 16	4, 8	0.5, 1
	7.6	E-SHV	1	32	32	64	16	128	8	64	2	1
5	7.6, 5.4	NE-SHV, TEM-1	7	16-64	32-64	2-16	1-16	2-16	1-8	4-16	0.03-0.13	0.06-0.5
	7.6	NE-SHV	4	16-64	32-64	1-16	0.5-16	2-16	2-16	2-16	0.03-0.13	0.06-0.5

^aE-SHV, SHV-type ESBL; NE-SHV, SHV-type non-ESBL.

^bAMC, amoxicillin and clavulanic acid; FOX, cefoxitin; CAZ, ceftazidime; CAZ + CLA, ceftazidime and clavulanic acid (2 μg/ml); CTX, cefotaxime; CTX + CLA, cefotaxime and clavulanic acid (2 μg/ml); ATM, aztreonam; FEP, cefepime; IPM, imipenem. The MIC values at which 50% of the isolates tested were inhibited (MIC₅₀) and MIC₉₀ values are shown in parentheses (MIC₅₀/MIC₉₀).

^cOnly 24 randomly selected DHA-1-producing isolates were investigated. PFGE, pulsed-field gel electrophoresis.