title: Characterization of an extended-spectrum beta-lactamase Enterobacter hormaechei nosocomial outbreak, and other Enterobacter hormaechei misidentified as Cronobacter (Enterobacter) sakazakii.
abstract: Enterobacter hormaechei is a Gram-negative bacterium within the Enterobacter cloacae complex, and has been shown to be of clinical significance by causing nosocomial infections, including sepsis. Ent. hormaechei is spread via horizontal transfer and is often associated with extended-spectrum beta-lactamase production, which increases the challenges associated with treatment by limiting therapeutic options. This report considers 10 strains of Ent. hormaechei (identified by 16S rDNA sequencing) that had originally been identified by phenotyping as Cronobacter (Enterobacter) sakazakii. Seven strains were from different neonates during a nosocomial outbreak in a California hospital. PFGE analysis revealed a clonal relationship among six of the seven isolates and therefore a previously unrecognized Ent. hormaechei outbreak had occurred over a three-month period. Antibiotic-resistance profiles were determined and extended-spectrum beta-lactamase activity was detected. The association of the organism with powdered infant formula, neonatal hosts and Cr. sakazakii suggested that the virulence of these organisms may be similar. Virulence traits were tested and all strains were shown to invade both gut epithelial (Caco-2) and blood-brain barrier endothelial cells (rBCEC4), and to persist in macrophages (U937). Due to misidentification we suggest that Ent. hormaechei may be an under-reported cause of bacterial infection, especially in neonates. Also, its isolation from various sources, including powdered infant milk formula, makes it a cause for concern and merits further investigation.
authors.affiliation: Nottingham Trent University, School of Science and Technology, Clifton Lane, Nottingham NG11 8NS, UK.
authors.forename: Stacy M
authors.initials: SM
authors.lastname: Townsend
authors.affiliation: Nottingham Trent University, School of Science and Technology, Clifton Lane, Nottingham NG11 8NS, UK.
authors.forename: Edward
authors.initials: E
authors.lastname: Hurrell
authors.affiliation: Nottingham Trent University, School of Science and Technology, Clifton Lane, Nottingham NG11 8NS, UK.
authors.forename: Juncal
authors.initials: J
authors.lastname: Caubilla-Barron
authors.affiliation: Nottingham Trent University, School of Science and Technology, Clifton Lane, Nottingham NG11 8NS, UK.
authors.forename: Catherine
authors.initials: C
authors.lastname: Loc-Carrillo
authors.affiliation: Nottingham Trent University, School of Science and Technology, Clifton Lane, Nottingham NG11 8NS, UK.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Forsythe
mesh_terms: D000818:Animals; D015373:Bacterial Typing Techniques; D018938:Caco-2 Cells; D002140:California; D044083:Cronobacter sakazakii / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification / Q000472:pathogenicity; D003428:Cross Infection / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology; D004269:DNA, Bacterial / Q000032:analysis / Q000302:isolation & purification; D003951:Diagnostic Errors; D004196:Disease Outbreaks; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D042783:Endothelial Cells; D004754:Enterobacter / Q000145:classification* / Q000187:drug effects / Q000302:isolation & purification / Q000472:pathogenicity; D004756:Enterobacteriaceae Infections / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology; D006801:Humans; D007231:Infant, Newborn; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010641:Phenotype; D051381:Rats; D017422:Sequence Analysis, DNA; D020298:U937 Cells; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D004269:DNA, Bacterial; D001618:beta-Lactamases