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Int J Antimicrob Agents. 2013 Dec;42(6):500-6. doi: 10.1016/j.ijantimicag.2013.08.005. Epub 2013 Sep 10.

Detection of chromosomal blaCTX-M-15 in Escherichia coli O25b-B2-ST131 isolates from the Kinki region of Japan.

Author information

1
Department of Biomedical Informatics, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan; Japan Science and Technology Agency/Japan International Cooperation Agency, Science and Technology Research Partnership for Sustainable Development (JST/JICA, SATREPS), Japan; Laboratory of Microbiology, School of Health Sciences, Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan. Electronic address: hiraii@med.u-ryukyu.ac.jp.

Abstract

Escherichia coli O25b-B2-ST131 isolates harbouring bla(CTX-M-15) are distributed worldwide. The bla(CTX-M-15) transposition unit has often been found on plasmids and the genetic contexts have been examined; however, less is known about the frequency and contexts of the bla(CTX-M-15) transposition unit on the chromosome. This study was performed to determine the chromosomal location of the bla(CTX-M-15) transposition unit and to analyse the molecular structure of the region surrounding the bla(CTX-M-15) transposition unit in E. coli O25b-B2-ST131 isolates. Twenty-two E. coli O25b-B2-ST131 strains harbouring bla(CTX-M-15) that had been isolated from university hospital patients and nursing home residents in the Kinki region of Japan were examined. Inverse PCR (iPCR) targeting bla(CTX-M-15) was performed to classify the molecular structure of the region surrounding the bla(CTX-M-15) transposition unit. The isolates were classified into nine types (types A-I) considering the iPCR results; type A was the most prevalent type (13/22 isolates). Sequences of the iPCR-amplified DNA fragments showed that the bla(CTX-M-15) transposition unit consisted of ISEcp1, bla(CTX-M-15) and orf477Δ. A homology search of the obtained sequences showed that the bla(CTX-M-15) transposition unit was inserted into different chromosomal regions in eight of the nine classified types. Although 21 of the 22 E. coli isolates possessed chromosomally located bla(CTX-M-15) transposition units, clonal spread was not evident on pulsed-field gel electrophoresis (PFGE) analysis. Taken together, these data indicate that certain E. coli O25b-B2-ST131 strains harbouring chromosomal bla(CTX-M-15) have emerged and spread in the Kinki region of Japan.

KEYWORDS:

CTX-M-type extended-spectrum β-lactamase; Chromosomal location; ESBL; Escherichia coli O25b-B2-ST131; bla(CTX-M-15)

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