Effects of Phenotype and Genotype on Methods for Detection of Extended-Spectrum-β-Lactamase-Producing Clinical Isolates of Escherichia coli and Klebsiella pneumoniae in Norway

DOI: 10.1128/JCM.01319-06

Article Figures & Data

TABLE 1.

PCR primers used in this study

Amplicon	Primer sequence (5′ to 3′)	Size of amplicon (bp)	Annealing temp (°C)	Reference or source
16S rRNA gene	AGA GTT TGA TCM TGG CTC AG	∼1,500	55	27a
	ACG GHT ACC TTG TTA CGA CTT
bla _TEM	ATG AGT ATT CAA CAT TTC CG	858	50	This study
	CCA ATG CTT AAT CAG TGA GG
bla _SHV	ATG CGT TAT ATT CGC CTG TG	862	58	This study
	AGC GTT GCC AGT GCT CGA TC
bla _CTX _-M	SCS ATG TGC AGY ACC AGT AA	585	58	This study
	ACC AGA AYV AGC GGB GC

TABLE 3.

Evaluation of ESBL Etest performance in relation to ESBL genotypes in 50 E. coli and 19 K. pneumoniae strains

ESBL Etest result with^a:					No. of strains with indicated genotype
ESBL Etest result with^a:				E. coli					K. pneumoniae
CTX	CAZ	FEP	bla_CTX-M-15 (n = 23)	bla_CTX-M-9 (n = 15)	Other (n = 12)	bla_SHV (n = 15)	bla_CTX_-M (n = 3)	Other (n = 1)
+	+	+	23	14^f	11	12	3	1^g
+	−	+	0	1	1^b	1^c	0	0
−	+	+	0	0	0	1^d	0	0
−	+	−	0	0	0	1^e	0	0

↵ a +, positive ESBL Etest; −, negative ESBL Etest.
↵ b bla _CTX-M-1 (CAZ/CAZ-CLA ratio, 5:3) (K4-55).
↵ c bla _SHV-2 (K5-30).
↵ d bla _SHV-28 (K2-79).
↵ e bla _SHV-28 (K4-61).
↵ f Includes bla_CTX-M-16 (K4-70).
↵ g bla _TEM-52 (K2-31).

TABLE 4.

Evaluation of the performance of the combined disk method in relation to ESBL genotype in 50 E. coli and 19 K. pneumoniae strains

Combined disk method results with^a:					No. of strains with indicated genotype
Combined disk method results with^a:				E. coli					K. pneumoniae
CTX	CAZ	CPD	bla_CTX-M-15 (n = 23)	bla_CTX-M-9 (n = 15)	Other (n = 12)	bla_SHV (n = 15)	bla_CTX_-M (n = 3)	Other (n = 1)
+	+	+	22	1^e	6	12	3	1^f
+	−	+	1	14	6^b	2^c	0	0
−	−	−	0	0	0	1^d	0	0

↵ a +, positive combined disk test; −, negative combined disk test.
↵ b bla _TEM-128 (n = 2; K4-71 and K5-25), bla_CTX-3/32/22 (K5-58), bla_CTX-3/22 (K8-8) (n = 2), and bla_CTX-M-1 (n = 2).
↵ c bla _SHV-2 (K5-30) and bla_SHV-2a (K2-36).
↵ d bla _SHV-28 (K2-79). The difference between the ceftazidime disk diameter with clavulanate and the one without was 3 mm (24 versus 21 mm).
↵ e bla _CTX-M-16 (K4-70).
↵ f bla _TEM-52 (K2-31).

TABLE 5.

MIC means and ranges for oxyimino-cephalosporins and aztreonam in relation to ESBL genogroups of E. coli and K. pneumoniae

↵ a The value 256 μg/ml has been used to calculate the mean for strains displaying a MIC of >256 mg/liter. For simplicity, mean values are also given for genotypes represented by only one strain.
↵ b The bla_CTX-M-9 genogroup but without the single bla_CTX-M-16 strain.
↵ c One bla_SHV-5 isolate (K4-49) displayed an aberrant phenotype. For this isolate, the CPD, CAZ, and aztreonam MICs were 256 mg/liter; the CTX MIC was 64 mg/liter; and the cefoxitin MIC was 12 mg/liter.