Molecular characteristics of extended-spectrum beta-lactamases and qnr determinants in Enterobacter species from Japan.
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.
Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan. kanamori@med.tohoku.ac.jp
Hajime
H
Kanamori
Hisakazu
H
Yano
Yoichi
Y
Hirakata
Ayako
A
Hirotani
Kazuaki
K
Arai
Shiro
S
Endo
Sadahiro
S
Ichimura
Miho
M
Ogawa
Masahiro
M
Shimojima
Tetsuji
T
Aoyagi
Masumitsu
M
Hatta
Mitsuhiro
M
Yamada
Yoshiaki
Y
Gu
Koichi
K
Tokuda
Hiroyuki
H
Kunishima
Miho
M
Kitagawa
Mitsuo
M
Kaku
D016521:Electrophoresis, Gel, Pulsed-Field; D004754:Enterobacter / Q000201:enzymology*; D007564:Japan; D046529:Microscopy, Electron, Transmission; D001618:beta-Lactamases / Q000235:genetics*
D001618:beta-Lactamases