title: Detection and characterization of extended-spectrum beta-lactamases among bloodstream isolates of Enterobacter spp. in Hong Kong, 2000-2002.
abstract: OBJECTIVE
  A total of 139 consecutive and non-duplicate bloodstream isolates of Enterobacter spp. collected from inpatients in Hong Kong during 2000-2002 were studied for production of extended-spectrum beta-lactamases (ESBLs).
  
  
  METHODS
  All isolates were evaluated by the modified double-disc synergy test (m-DDST), the combined disc method (CDM) and the three-dimensional (3D) test. The m-DDST and CDM were modified by the use of cefepime discs. beta-Lactamases were characterized by isoelectric focusing and PCR sequencing using specific primers.
  
  
  RESULTS
  ESBLs were identified in nine isolates (overall 6.5%), including seven of 39 (17.9%) Enterobacter hormaechei, one of 27 (3.7%) Enterobacter aerogenes and the only Enterobacter intermedius strain. The E. intermedius strain was positive only in the 3D test but not in the other two tests. The other eight strains were positive in all three tests. No ESBL was detected in the other species, including non-hormaechei members of the Enterobacter cloacae complex (n=61), Enterobacter agglomerans (n=7), Enterobacter gergoviae (n=4) and Enterobacter sakazakii (n=1). The ESBL content included five different CTX-M enzymes (CTX-M-9, CTX-M-13, CTX-M-14, CTX-M-24 and a novel CTX-M-2-like beta-lactamase), SHV-12 (n=2) and unidentifiable ESBLs with a pI of 7.7 or 7.9 in two strains. The seven ESBL-producing E. hormaechei were genotyped by pulsed-field gel electrophoresis and were found to be unrelated to each other. In three of the CTX-M-producing strains, ISEcp1-like elements, including promoters for the beta-lactamase gene, were found.
  
  
  CONCLUSIONS
  Our data underscore the diversity of CTX-M enzymes among Enterobacter spp. in Hong Kong.
authors.affiliation: Division of Infectious Diseases, Department of Microbiology and Centre of Infection, United Christian Hospital, University of Hong Kong, Hong Kong SAR, China. plho@hkucc.hku.hk
authors.forename: P L
authors.initials: PL
authors.lastname: Ho
authors.forename: Ricky H L
authors.initials: RH
authors.lastname: Shek
authors.forename: K H
authors.initials: KH
authors.lastname: Chow
authors.forename: R S
authors.initials: RS
authors.lastname: Duan
authors.forename: Gannon C
authors.initials: GC
authors.lastname: Mak
authors.forename: Eileen L
authors.initials: EL
authors.lastname: Lai
authors.forename: W C
authors.initials: WC
authors.lastname: Yam
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Tsang
authors.forename: W M
authors.initials: WM
authors.lastname: Lai
mesh_terms: D016470:Bacteremia / Q000382:microbiology*; D004754:Enterobacter / Q000201:enzymology*; D006723:Hong Kong; D006801:Humans; D008826:Microbial Sensitivity Tests; D013997:Time Factors; D001618:beta-Lactamases / Q000032:analysis* / Q000235:genetics
chemical_list: C456080:beta-lactamase CTX-M-14; D001618:beta-Lactamases