Genomic diversity within the Enterobacter cloacae complex.
BACKGROUND
Isolates of the Enterobacter cloacae complex have been increasingly isolated as nosocomial pathogens, but phenotypic identification of the E. cloacae complex is unreliable and irreproducible. Identification of species based on currently available genotyping tools is already superior to phenotypic identification, but the taxonomy of isolates belonging to this complex is cumbersome.


RESULTS
This study shows that multilocus sequence analysis and comparative genomic hybridization based on a mixed genome array is a powerful method for studying species assignment within the E. cloacae complex. The E. cloacae complex is shown to be evolutionarily divided into two clades that are genetically distinct from each other. The younger first clade is genetically more homogenous, contains the Enterobacter hormaechei species and is the most frequently cultured Enterobacter species in hospitals. The second and older clade consists of several (sub)species that are genetically more heterogeneous. Genetic markers were identified that could discriminate between the two clades and cluster 1.


CONCLUSIONS
Based on genomic differences it is concluded that some previously defined (clonal and heterogenic) (sub)species of the E. cloacae complex have to be redefined because of disagreements with known or proposed nomenclature. However, further improved identification of the redefined species will be possible based on novel markers presented here.
Paauw
Armand
A
Department of Medical Microbiology, University Medical Centre Utrecht, Utrecht, The Netherlands.
Caspers
Martien P M
MP
Schuren
Frank H J
FH
Leverstein-van Hall
Maurine A
MA
Delétoile
Alexis
A
Montijn
Roy C
RC
Verhoef
Jan
J
Fluit
Ad C
AC
D001426:Bacterial Proteins / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D016972:Enterobacter cloacae / Q000145:classification / Q000235:genetics*; D014644:Genetic Variation; D016680:Genome, Bacterial; D005838:Genotype; D009693:Nucleic Acid Hybridization; D010802:Phylogeny; D017422:Sequence Analysis, DNA
D001426:Bacterial Proteins; D004269:DNA, Bacterial