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Journal of Clinical Microbiology, January 2008, p. 103-108, Vol. 46, No. 1
0095-1137/08/$08.00+0     doi:10.1128/JCM.01542-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Molecular Epidemiology of Escherichia coli Producing Extended-Spectrum β-Lactamases Isolated in Rome, Italy

Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Rome, Italy,¹ Department of Science and Public Health-Microbiology, University of Rome La Sapienza, Rome, Italy²

Received 2 August 2007/ Returned for modification 16 August 2007/ Accepted 17 October 2007

Escherichia coli strains producing extended-spectrum β-lactamases (ESBLs) are a major problem in many different hospitals worldwide, causing outbreaks as well as sporadic infections. The prevalence of Escherichia coli ESBL producers was analyzed in a surveillance study performed on the population attending the Policlinico Umberto I, the largest university hospital in Rome, Italy. We also investigated genotypes, pathogenicity islands, and plasmids in the ESBL-positive E. coli isolates as further markers that are useful in describing the epidemiology of the infections. In this survey, 163 nonreplicate isolates of Escherichia coli were isolated from patients from 86 different wards, and 28 were confirmed as ESBL producers. A high prevalence (26/28) of CTX-M-15 producers was observed within the bacterial population circulating in this hospital, and the dissemination of this genetic trait was associated with the spread of related strains; however, these do not have the characteristics of a single epidemic clone spreading. The dissemination was also linked to horizontal transfer among the prevalent E. coli genotypes of multireplicon plasmids showing FIA, FIB, and FII replicons in various combinations, which are well adapted to the E. coli species. The analysis of related bacteria suggests a probable interpatient transmission occurring in several wards, causing small outbreaks.

Published ahead of print on 24 October 2007.

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