title: [Emergence of CTX-M-12 and A Novel CTX-M Type Extended-Spectrum beta-Lactamaseproducing Klebsiella pneumoniae.].
abstract: BACKGROUND
  The aims of this study were to survey the nation-wide susceptibilities of Klebsiella pneumoniae isolates against ceftazidime and cefotaxime and to determine the prevalence of class A extended-spectrum beta-lactamases (ESBLs).
  
  
  METHODS
  During the period of February to July 2004, K. pneumoniae isolates intermediate or resistant to ceftazidime and/or cefotaxime were collected from 12 hospitals in Korea. Antimicrobial susceptibilities were determined by the disk diffusion and the agar dilution methods and ESBL-production was by double-disk synergy test. Ceftazidime or cefotaxime-resistance determinants of the ESBLproducers were transfered to Escherichia coli J53 by transconjugation. Searches for class A ESBL genes were performed by PCR amplication.
  
  
  RESULTS
  Among 212 clinical K. pneumoniae isolates, 172 (81%) isolates showed positive results in double-disk synergy test; the most prevalent ESBL was SHV-12 (n=104). Genes encoding ESBLs including SHV-2 (n=6), SHV-2a (n=17), CTX-M-3 (n=18), CTX-M-9 (n=6), CTX-M-12 (n=1), CTX-M- 14 (n=27), CTX-M-15 (n=3), and a novel CTX-M-type beta-lactamases were also detected.
  
  
  CONCLUSIONS
  It is concluded that diversity of ESBLs in K. pneumoniae isolates are increasing in Korea. CTX-M-12 has never been reported in Asia, and a novel CTX-M-type ESBL has emerged.
authors.affiliation: Department of Laboratory Medicine, Kosin University College of Medicine, Busan, Korea. kscpjsh@ns.kosinmed.or.kr.
authors.forename: Il Kwon
authors.initials: IK
authors.lastname: Bae
authors.forename: Seok Hoon
authors.initials: SH
authors.lastname: Jeong
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Lee
authors.forename: Dongeun
authors.initials: D
authors.lastname: Yong
authors.forename: Jongwook
authors.initials: J
authors.lastname: Lee
authors.forename: Seong Geun
authors.initials: SG
authors.lastname: Hong
authors.forename: Eui Chong
authors.initials: EC
authors.lastname: Kim
authors.forename: Yeon Jun
authors.initials: YJ
authors.lastname: Park
authors.forename: Jung Oak
authors.initials: JO
authors.lastname: Kang
authors.forename: Young
authors.initials: Y
authors.lastname: Uh
authors.forename: Jong Hee
authors.initials: JH
authors.lastname: Shin
authors.forename: Wee Gyo
authors.initials: WG
authors.lastname: Lee
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Ahn
authors.forename: Sung Hee
authors.initials: SH
authors.lastname: Lee
authors.forename: Gun Jo
authors.initials: GJ
authors.lastname: Woo
authors.forename: Hyo Sun
authors.initials: HS
authors.lastname: Kwak