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Chromosomal ampC mutations in cefpodoxime-resistant ESBL-negative uropathogenic escherichia coli

Lawrance, L. M.; Arnold, D. L.; Moore, P. C.L.; Lewis, J. A.; Moore, P. M.; Arnold, Dawn L.; Lawrance, Lynne


L. M. Lawrance

D. L. Arnold

P. C.L. Moore

J. A. Lewis

P. M. Moore

Dawn L. Arnold

Lynne Lawrance
Senior Lecturer in Medical Microbiology


AmpC beta-lactamase is an enzyme commonly produced by Escherichia coli that causes resistance to cephalosporins and penicillins. Enzyme production is controlled by the strength of the promoter encoded by the chromosomal ampC gene, with the level of production affected by the presence of certain mutations in this region. This study sets out to determine the prevalence of ampC promoter mutations present in a group of uropathogenic E. coli strains. A total of 50 clinical strains of E. coli were collected from urine samples between June 2011 and November 2011. Strains were investigated for the presence of mutations in the chromosomal ampC promoter region by amplification and sequencing of a 271 bp product. The presence of ampC-carrying plasmids derived from other species was also determined, to exclude these from further analysis. ampC-carrying plasmids were found in 10 of the 50 strains, all of which were of the CIT-type. Analysis of the chromosomal ampC promoter region in the 40 remaining strains showed mutations at 16 different positions, with 18 different genotype patterns detected overall. The most common ampC chromosomal mutation, present in 25 of 40 strains, was a T?A transition at position -32. This mutation has been shown by others to increase enzyme production by up to 46-fold. Altogether, three separate mutations (-32, -42 and -13ins) were present in 90% of the 40 non-plasmid strains, indicating a strong association with the resistance observed. It appears, therefore, that the majority of AmpC-mediated resistance in E. coli can be accounted for by just three point mutations in the chromosome.


Lewis, J. A., Moore, P. M., Arnold, D. L., & Lawrance, L. (2015). Chromosomal ampC mutations in cefpodoxime-resistant ESBL-negative uropathogenic escherichia coli. British Journal of Biomedical Science, 72(1), 7-11.

Journal Article Type Article
Acceptance Date Feb 19, 2015
Publication Date Jan 1, 2015
Journal British Journal of Biomedical Science
Print ISSN 0967-4845
Peer Reviewed Peer Reviewed
Volume 72
Issue 1
Pages 7-11
Keywords ampC beta-lactamase, cephalosporins, drug resistance, microbial, escherichia coli
Public URL
Publisher URL
Additional Information Additional Information : This is the submitted version of an article published in British Journal of Biomedical Science, January 2015. The published version is available at British Journal of Biomedical Science


BJBS Article - Jan 2015 - v4.1.docx (161 Kb)

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