title: First outbreak of multidrug-resistant Klebsiella pneumoniae producing both SHV-12-type extended-spectrum beta-lactamase and DHA-1-type AmpC beta-lactamase at a Korean hospital.
abstract: OBJECTIVE
  Coexistence of different classes of beta-lactamases in a single bacterial isolate may pose diagnostic and therapeutic challenges. We investigated a spread of Klebsiella pneumoniae isolates co-producing an AmpC beta-lactamase and an extended-spectrum beta-lactamase (ESBL) in a university hospital.
  
  
  METHODS
  Over a three-month period, a total of 11 K. pneumoniae isolates, which exhibited resistance to cefotaxime, aztreonam, and cefoxitin, were isolated. These isolates showed positive to ESBLs by double disk tests. Minimal inhibitory concentrations (MICs) were determined by broth microdilution testing. All isolates were examined by isoelectric focusing, PCR and sequence analysis to identify bla(SHV) and bla(DHA), and molecular typing by pulsed-field gel electrophoresis (PFGE).
  
  
  RESULTS
  All 11 isolates were highly resistant (MIC, > or = 128microg/ml) to ceftazidime, aztreonam, and cefoxitin, while they were susceptible (MIC, < or = 2microg/ml) to imipenem. The bla(SHV-12) and bla(DHA-1) genes were detected by PCR and sequence analysis. PFGE revealed a similar pattern in 10 of the 11 strains tested.
  
  
  CONCLUSIONS
  This is the first outbreak report of K. pneumoniae in Korea which co-produced SHV-12 and DHA-1 beta-lactamase, and we suggest a clonal spread of multidrug-resistant K. pneumoniae at a hospital.
authors.affiliation: Department of Laboratory Medicine, Korean University Medical College, Seoul, Korea.
authors.forename: Kyoung Ho
authors.initials: KH
authors.lastname: Roh
authors.forename: Young
authors.initials: Y
authors.lastname: Uh
authors.forename: Jae-Seok
authors.initials: JS
authors.lastname: Kim
authors.forename: Han-Sung
authors.initials: HS
authors.lastname: Kim
authors.forename: Dong Hoon
authors.initials: DH
authors.lastname: Shin
authors.forename: Wonkeun
authors.initials: W
authors.lastname: Song
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004196:Disease Outbreaks; D004198:Disease Susceptibility; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D005838:Genotype; D006761:Hospitals; D006801:Humans; D007710:Klebsiella Infections / Q000453:epidemiology* / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D007723:Korea; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D001618:beta-Lactamases / Q000145:classification* / Q000235:genetics / Q000378:metabolism*
chemical_list: D001618:beta-Lactamases