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Antimicrobial Agents and Chemotherapy, June 2007, p. 1946-1955, Vol. 51, No. 6
0066-4804/07/$08.00+0     doi:10.1128/AAC.01412-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Spread of Extended-Spectrum ß-Lactamase CTX-M-Producing Escherichia coli Clinical Isolates in Community and Nosocomial Environments in Portugal{triangledown}

Nuno Mendonça, Joana Leitão, Vera Manageiro, Eugénia Ferreira, the Antimicrobial Resistance Surveillance Program in Portugal, Manuela Caniça,*

Antibiotic Resistance Unit, Centre of Bacteriology, National Institute of Health Dr. Ricardo Jorge, Lisbon, Portugal

Received 12 November 2006/ Returned for modification 18 December 2006/ Accepted 14 March 2007

Of the 181 unduplicated Escherichia coli strains isolated in nine different hospitals in three Portuguese regions, 119 were extended-spectrum ß-lactamase (ESBL)-CTX-M producers and were selected for phenotype and genotype characterization. CTX-M producer strains were prevalent among community-acquired infections (56%), urinary tract infections (76%), and patients ≥60 years old (76%). In MIC tests, all strains were resistant to cefotaxime, 92% were resistant to ceftazidime, 93% were resistant to quinolones, 89% were resistant to aminoglycoside, and 26% were resistant to trimethoprim-sulfamethoxazole; all strains were sensitive to carbapenems, and 92% of the strains had a multidrug resistance phenotype. Molecular methods identified 109 isolates harboring a blaCTX-M-15 gene, 1 harboring the blaCTX-M-32 gene (first identification in the country), and 9 harboring the blaCTX-M-14 gene. All isolates presented the ISEcp1 element upstream from the blaCTX-M genes; one presented the IS903 element (downstream of blaCTX-M-14 gene), and none had the IS26 element; 85% carried blaTEM-1B, and 84% also carried a blaOXA-30. Genetic relatedness analysis based on pulsed-field gel electrophoresis defined five clusters and indicated that 76% of all isolates (from cluster IV) corresponded to a single epidemic strain. Of the 47 strains from one hospital, 41 belonged to cluster IV and were disseminated in three main wards. CTX-M-producing E. coli strains are currently a problem in Portugal, with CTX-M-15 particularly common. This study suggests that the horizontal transfer of blaCTX-M genes, mediated by plasmids and/or mobile elements, contributes to the dissemination of CTX-M enzymes to community and hospital environments. The use of extended-spectrum cephalosporins, quinolones, and aminoglycosides is compromised, leaving carbapenems as the therapeutic option for severe infections caused by ESBL producers.

* Corresponding author. Mailing address: Antibiotic Resistance Unit, National Institute of Health Dr. Ricardo Jorge, Av. Padre Cruz, 1649-016 Lisbon, Portugal. Phone: 351-217519246. Fax: 351-217519246. E-mail: manuela.canica{at}insa.min-saude.pt

{triangledown} Published ahead of print on 19 March 2007.

Antimicrobial Agents and Chemotherapy, June 2007, p. 1946-1955, Vol. 51, No. 6
0066-4804/07/$08.00+0     doi:10.1128/AAC.01412-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



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