title: Emergence of serotype K1Klebsiella pneumoniaeST23 strains co-producing the plasmid-mediated AmpC beta-lactamase DHA-1 and an extended-spectrum beta-lactamase in Korea.
abstract: BACKGROUND
  Serotype K1Klebsiella pneumoniaehas emerged as an important community pathogen causing various infections, including liver abscesses. Although serotype K1K. pneumoniaecommunity isolates have been reported as susceptible to most classes of antimicrobial agents, a few cases of infection caused by extended-spectrum beta-lactamase (ESBL)-producing serotype K1K. pneumoniaehave recently been reported in Asian countries. We identified three ESBL-producing strains of serotype K1K. pneumoniaeand conducted a molecular characterization of their drug resistance.
  
  
  METHODS
  Three ESBL-producing serotype K1K. pneumoniaeST23 strains were identified from strains in the Asian Bacterial Bank. Antimicrobial susceptibility testing was performed using the broth microdilution method, and ESBL production was tested by the double-disk synergy test and a confirmatory test. PCR was performed to detect the genes for plasmid-mediated ESBL and AmpC beta-lactamases.
  
  
  RESULTS
  All three strains were resistant to cefotaxime, ceftazidime, and piperacillin/tazobactam, and all were determined to be ESBL-producers. No known ESBL genes, includingblaSHV,blaTEM,blaCTX-M,blaGES,blaPER, andblaVEB, were detected among the three strains. Of all plasmid-mediated AmpC beta-lactamase (PAB) genes, includingblaDHA-1,blaCMY,blaFOX, andblaMOX, theblaDHA-1gene was detected in two of the strains. The PFGE patterns revealed that the two isolates carryingblaDHA-1were closely related (84% similarity).
  
  
  CONCLUSIONS
  No ESBL genes were detected among three ESBL-producing serotype K1K. pneumoniaeST23 strains. Two strains contained the PAB geneblaDHA-1. The emergence of resistant strains of community-origin serotype K1K. pneumoniaehas important implications for effective treatment and infection control practices.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Republic of Korea.
authors.forename: Hae Suk
authors.initials: HS
authors.lastname: Cheong
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-Ro, Gangnam-gu, Seoul, 06351 Republic of Korea ; Asia Pacific Foundation for Infectious Diseases (APFID), Seoul, Korea.
authors.forename: Doo Ryeon
authors.initials: DR
authors.lastname: Chung
authors.affiliation: Asia Pacific Foundation for Infectious Diseases (APFID), Seoul, Korea.
authors.forename: Chaeyoeng
authors.initials: C
authors.lastname: Lee
authors.affiliation: Asia Pacific Foundation for Infectious Diseases (APFID), Seoul, Korea.
authors.forename: So Hyun
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-Ro, Gangnam-gu, Seoul, 06351 Republic of Korea.
authors.forename: Cheol-In
authors.initials: CI
authors.lastname: Kang
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-Ro, Gangnam-gu, Seoul, 06351 Republic of Korea.
authors.forename: Kyong Ran
authors.initials: KR
authors.lastname: Peck
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-Ro, Gangnam-gu, Seoul, 06351 Republic of Korea ; Asia Pacific Foundation for Infectious Diseases (APFID), Seoul, Korea.
authors.forename: Jae-Hoon
authors.initials: JH
authors.lastname: Song
keywords: AmpC beta-lactamase; Extended-spectrum beta-lactamase; Klebsiella pneumoniae