Third-generation cephalosporin resistance conferred by a chromosomally encoded blaCMY-23 gene in the Escherichia coli ST131 reference strain EC958

Phan, Minh-Duy, Peters, Kate M., Sarkar, Sohinee, Forde, Brian M., Lo, Alvin W., Stanton-Cook, Mitchell, Roberts, Leah W., Upton, Mathew, Beatson, Scott A. and Schembri, Mark A. (2015) Third-generation cephalosporin resistance conferred by a chromosomally encoded blaCMY-23 gene in the Escherichia coli ST131 reference strain EC958. Journal of Antimicrobial Chemotherapy, 70 7: 1969-1972. doi:10.1093/jac/dkv066


Author Phan, Minh-Duy
Peters, Kate M.
Sarkar, Sohinee
Forde, Brian M.
Lo, Alvin W.
Stanton-Cook, Mitchell
Roberts, Leah W.
Upton, Mathew
Beatson, Scott A.
Schembri, Mark A.
Title Third-generation cephalosporin resistance conferred by a chromosomally encoded blaCMY-23 gene in the Escherichia coli ST131 reference strain EC958
Formatted title
Third-generation cephalosporin resistance conferred by a chromosomally encoded blaCMY-23 gene in the Escherichia coli ST131 reference strain EC958
Journal name Journal of Antimicrobial Chemotherapy   Check publisher's open access policy
ISSN 0305-7453
1460-2091
Publication date 2015-03-01
Year available 2015
Sub-type Article (original research)
DOI 10.1093/jac/dkv066
Open Access Status Not Open Access
Volume 70
Issue 7
Start page 1969
End page 1972
Total pages 4
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Language eng
Formatted abstract
Objectives Escherichia coli ST131 is a globally disseminated MDR clone originally identified due to its association with the blaCTX-M-15 gene encoding an ESBL. It is thus assumed that blaCTX-M-15 is the major determinant for resistance to β-lactam antibiotics in this clone. The complete sequence of EC958, a reference strain for E. coli ST131, revealed that it contains a chromosomally located blaCMY-23 gene with an upstream ISEcp1 element as well as several additional plasmid-encoded β-lactamase genes. Here, we examined the genetic context of the blaCMY-23 element in EC958 and other E. coli ST131 strains and investigated the contribution of blaCMY-23 to EC958 resistance to a range of β-lactam antibiotics.

Methods The genetic context of blaCMY-23 and its associated mobile elements was determined by PCR and sequencing. Antibiotic susceptibility testing was performed using Etests. The activity of the blaCMY-23 promoter was assessed using lacZ reporter assays. Mutations were generated using λ-Red-recombination.

Results The genetic structure of the ISEcp1-IS5-blaCMY-23 mobile element was determined and localized within the betU gene on the chromosome of EC958 and five other E. coli ST131 strains. The transcription of blaCMY-23, driven by a previously defined promoter within ISEcp1, was significantly higher than other β-lactamase genes and could be induced by cefotaxime. Deletion of the blaCMY-23 gene resulted in enhanced susceptibility to cefoxitin, cefotaxime and ceftazidime.

Conclusions This is the first known report to demonstrate the chromosomal location of blaCMY-23 in E. coli ST131. In EC958, CMY-23 plays a major role in resistance to third-generation cephalosporins and cephamycins.
Keyword E. coli SR131
Antibiotic resistance
AmpC β-lactamases
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2016 Collection
School of Chemistry and Molecular Biosciences
 
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Created: Fri, 27 Mar 2015, 21:12:14 EST by Mrs Louise Nimwegen on behalf of School of Chemistry & Molecular Biosciences