Molecular Characteristics of Extended-Spectrum β-Lactamases in Clinical Isolates from Escherichia coli at a Japanese Tertiary Hospital

Hisakazu Yano, Mina Uemura, Shiro Endo, Hajime Kanamori, Shinya Inomata, Risako Kakuta, Sadahiro Ichimura, Miho Ogawa, Masahiro Shimojima, Noriomi Ishibashi, Tetsuji Aoyagi, Masumitsu Hatta, Yoshiaki Gu, Mitsuhiro Yamada, Koichi Tokuda, Hiroyuki Kunishima, Miho Kitagawa, Yoichi Hirakata, Mitsuo Kaku

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37 Citations (Scopus)


The prevalence of ESBL has been increasing worldwide. In this study, we investigated the molecular characteristics of ESBL among clinical isolates of Escherichia coli from a Japanese tertiary hospital. A total of 71 consecutive and nonduplicate clinical isolates of ESBL-positive E. coli collected at Tohoku University Hospital between January 2008 and March 2011 were studied. The antimicrobial susceptibility profile of these strains was determined. PCR and sequencing were performed to identify genes for β-lactamase (blaTEM, blaSHV, blaOXA-1-like, and blaCTX-M) and plasmid-mediated quinolone resistance determinants (PMQR). The isolates were also analyzed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Of the 71 strains, 68 were positive for CTX-M, 28 were positive for TEM, four were positive for OXA-1, and one was positive for SHV. Sequencing revealed that CTX-M-14 was the most prevalent (31/71), followed by CTX-M-27 (21/71) and then CTX-M-15 (9/71). Of the 28 TEM-positive strains, one was TEM-10 and the rest were TEM-1. One SHV-positive strain was SHV-12. The 21 CTX-M-27-producing isolates were divided into 14 unique PFGE types, while the 9 CTX-M-15 producers were divided into 8 types. Based on MLST, 9 CTX-M-14 procedures, 19 CTX-M-27 procedures, and 8 CTX-M-15 producers belonged to ST131. Thirty-five (94.6%) of the 37 ST131 E. coli strains showed resistance to levofloxacin, which was a higher rate than among non-ST131 strains (63.6%). Among ESBL-producing isolates, one, two, and six possessed qnrB, qnrS, qepA, and aac(6′)-Ib-cr, respectively. Of the 6 isolates with aac(6′)-Ib-cr, 4 carried the CTX-M-15 gene. Our data suggest that CTX-M-15-producing E. coli ST131 has emerged as a worldwide pandemic clone, while CTX-M-27 (a variant of CTX-M-14) is also spreading among E. coli ST131 in Japan.

Original languageEnglish
Article numbere64359
JournalPloS one
Issue number5
Publication statusPublished - 2013 May 15

ASJC Scopus subject areas

  • General


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