PLoS ONE (Jan 2012)

Molecular characteristics of extended-spectrum beta-lactamases and qnr determinants in Enterobacter species from Japan.

  • Hajime Kanamori,
  • Hisakazu Yano,
  • Yoichi Hirakata,
  • Ayako Hirotani,
  • Kazuaki Arai,
  • Shiro Endo,
  • Sadahiro Ichimura,
  • Miho Ogawa,
  • Masahiro Shimojima,
  • Tetsuji Aoyagi,
  • Masumitsu Hatta,
  • Mitsuhiro Yamada,
  • Yoshiaki Gu,
  • Koichi Tokuda,
  • Hiroyuki Kunishima,
  • Miho Kitagawa,
  • Mitsuo Kaku

DOI
https://doi.org/10.1371/journal.pone.0037967
Journal volume & issue
Vol. 7, no. 6
p. e37967

Abstract

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The incidence of extended-spectrum β-lactamases (ESBLs) has been increasing worldwide, but screening criteria for detection of ESBLs are not standardized for AmpC-producing Enterobacteriaceae such as Enterobacter species. In this study, we investigated the prevalence of ESBLs and/or AmpC β-lactamases in Japanese clinical isolates of Enterobacter spp. and the association of plasmid-mediated quinolone resistance (PMQR) determinants with ESBL producers. A total of 364 clinical isolates of Enterobacter spp. collected throughout Japan between November 2009 and January 2010 were studied. ESBL-producing strains were assessed by the CLSI confirmatory test and the boronic acid disk test. PCR and sequencing were performed to detect CTX-M, TEM, and SHV type ESBLs and PMQR determinants. For ESBL-producing Enterobacter spp., pulsed-field gel electrophoresis (PFGE) was performed using XbaI restriction enzyme. Of the 364 isolates, 22 (6.0%) were ESBL producers. Seven isolates of Enterobacter cloacae produced CTX-M-3, followed by two isolates producing SHV-12. Two isolates of Enterobacter aerogenes produced CTX-M-2. Of the 22 ESBL producers, 21 had the AmpC enzyme, and six met the criteria for ESBL production in the boronic acid test. We found a significant association of qnrS with CTX-M-3-producing E. cloacae. The 11 ESBL-producing Enterobacter spp. possessing bla(CTX-M), bla(SHV), or bla(TEM) were divided into six unique PFGE types. This is the first report about the prevalence of qnr determinants among ESBL-producing Enterobacter spp. from Japan. Our results suggest that ESBL-producing Enterobacter spp. with qnr determinants are spreading in Japan.