Journal Article

Mechanisms of resistance to expanded-spectrum cephalosporins in <i>Escherichia coli</i> isolates recovered in a Spanish hospital

Laura Briñas, Marta Lantero, Isabel de Diego, María Alvarez, Myriam Zarazaga and Carmen Torres

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 56, issue 6, pages 1107-1110
Published in print December 2005 | ISSN: 0305-7453
Published online October 2005 | e-ISSN: 1460-2091 | DOI: http://dx.doi.org/10.1093/jac/dki370
Mechanisms of resistance to expanded-spectrum cephalosporins in Escherichia coli isolates recovered in a Spanish hospital

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Objectives: To characterize the β-lactamase genes of the expanded-spectrum cephalosporin-resistant Escherichia coli isolates recovered in a Spanish hospital during the March 2002–March 2003 period.

Methods: Thirty-four of the 1700 E. coli isolates recovered from unrelated patients in a Spanish hospital showed expanded-spectrum cephalosporin resistance. The presence of genes encoding TEM, SHV, CTX-M, CMY-2-type or FOX β-lactamases as well as the existence of mutations in the regulatory region of the chromosomal ampC gene were studied by PCR and sequencing in these 34 E. coli isolates.

Results: The following extended-spectrum β-lactamases (ESBLs) or plasmidic class C β-lactamase genes were detected (number of isolates): blaCTX-M-14 (14), blaCTX-M-9 (4), blaCTX-M-32 (1), blaTEM-52 (2), blaSHV-12 (3) and blaCMY-2 (2). The remaining eight isolates showed a mutation in the promoter/attenuator region of the ampC chromosomal gene at position −42, in combination with mutations at positions −18, −1 and +58. The blaTEM-1 gene was also detected in 12 of the ESBL-producing isolates, in both CMY-2-producing isolates and in four of the eight isolates that showed a mutation at position −42 of the ampC promoter. Other mutations in the promoter/attenuator region were detected in association with ESBL or CMY-2 genes, such as the combination −18, −1 and +58, −28 and +58, or +22, +26, +27 and +32. No clonal relationship was found among the CTX-M-producing E. coli isolates by PFGE with XbaI enzyme.

Conclusions: Approximately 1.5% of the E. coli isolates of our hospital harboured ESBL genes, those of the CTX-M-9 group being the most common ones.

Keywords: E. coli; ESBLs; class C β-lactamases; Spain

Journal Article.  2087 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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