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

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

Strain Sample Motilityb Ornithine decarboxylaseb API Code API Identificationc Vitek2d Phoenixd tDNA-PCRe Clonef
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
  1. 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.
  2. b: +, positive; -, negative; (-), negative after standard incubation time, only positive after subculturing and/or retesting with prolonged incubation periods.
  3. c: Weak: Weak identification with possibilities: E. aerogenes, K. pneumoniae or R. planticola.
  4. d: NT: not tested.
  5. e: * indicates that identification was confirmed by 16S rDNA sequence analysis.
  6. f: Clonal relationships were determined using RAPD-analysis.