Extended-Spectrum β-lactamase (ESBL) producing Enterobacter aerogenes phenotypically misidentified as Klebsiella pneumoniae or K. terrigena

Table 1 Clinical data and phenotypic and genotypic identification results of the Klebsiella pneumoniae and Enterobacter aerogenes isolates used in this study

Strain	Sample	Motility^b	Ornithine decarboxylase^b	API Code	API Identification^c	Vitek2^d Phoenix^d	tDNA-PCR^e	Clone^f
Group 1
LBV268		+	+	5305773	E. aerogenes	E. aerogenes	E. aerogenes	BEI
MN1	Aspirate	+	+	5305773	E. aerogenes	NT	E. aerogenes	BEII
BEI 166		+	+	5305773	E. aerogenes	NT	E. aerogenes	BEI
BEII 169		+	+	5305773	E. aerogenes	NT	E. aerogenes	BEII
Group 2
BG	Blood culture	-	-	5005763	K. pneumoniae/K. terrigena	K. pneumoniae	K. pneumoniae	K1
DHJ2	Aspirate	-	-	5215773	K. pneumoniae	K. pneumoniae	K. pneumoniae	K2
Group 3
GA1	Wound	(-)	(-)	5205773	Weak	NT	E. aerogenes	BEI
GA2	Urine	(-)	(-)	5205773	Weak	NT	E. aerogenes	BEI
GA3	Urine	(-)	(-)	5205773	Weak	K. pneumoniae	E. aerogenes*	BEI
MN2	Ascites	(-)	(-)	5205773	Weak	K. pneumoniae	E. aerogenes	BEI
MN3	Urine	(-)	(-)	5205773	Weak	NT	E. aerogenes*	BEI
VGM	Sputum	(-)	(-)	5205773	Weak	K. pneumoniae	E. aerogenes	BEII-related
DHJ1	Urine	(-)	(-)	5205753	No identification	NT	E. aerogenes*	BEII-related
DHJ3	Blood culture	(-)	(-)	5205753	No identification	NT	E. aerogenes	BEII-related
RA	Throat isolate	(-)	(-)	5204673	K. terrigena	NT	E. aerogenes*	Non-related
DBH	Urine	(-)	(-)	5204673	K. terrigena	NT	E. aerogenes*	BEI

a: Data for genuine E. aerogenes isolates are presented first (group 1). Clinical isolate LBV268 was used as control for analysis on automated phenotypical identification systems. The isolates BEI 166 and BEII 169 were shown previously [4] to belong to the two major E. aerogenes clones (BEI and BEII) in Belgium. Group 2 presents data for genuine K. pneumoniae. Clinical isolate BG was used as control for analysis on automated phenotypical identification systems. The third group presents the data for the phenotypically aberrant E. aerogenes isolates.
b: +, positive; -, negative; (-), negative after standard incubation time, only positive after subculturing and/or retesting with prolonged incubation periods.
c: Weak: Weak identification with possibilities: E. aerogenes, K. pneumoniae or R. planticola.
d: NT: not tested.
e: * indicates that identification was confirmed by 16S rDNA sequence analysis.
f: Clonal relationships were determined using RAPD-analysis.

ISSN: 1471-2180