Epidemiology and molecular characterisation of clinical isolates of Escherichia coli producing extended-spectrum b-lactamases from Rome, Italy

Abstract number: 1733_517

Carattoli A., Garcia A., Varesi P., Fortini D., Gerardi S., Penni A., Mancini C., Giordano A.

Objectives: Extended-spectrum b-lactamase (ESBL)-producing Escherichia coli are an emergent cause of infections in the Policlinico Umberto I, a large University hospital of Rome (1500 beds), making more difficult managing carrier patients. Our aim is to analyse the epidemiology and to characterise the E. coli ESBL producers in the population attending our hospital.

Methods: A perspective study was carried out from 1st April to 15th September 2006. A total number of 5674 various clinical samples were sent for bacterial isolation to the Microbiology Laboratory from 51 different wards, for suspected hospital acquired infections. 209 E. coli strains were isolated from 166 inpatients. Antimicrobial susceptibilities were carried out by the VITEK 2 system. Double-disk synergy test were used for the confirmation of ESBL producers. ESBL genes were characterised by PCR and sequencing. Clonal relationships among the isolates were determined by ERIC-PCR. Plasmid extraction was performed by alkaline lyses. Plasmids were typed by the PCR-based replicon typing method.

Results: A total of 51 non-repetitive (one for each patient) E. coli ESBL positive strains were obtained indicating a prevalence of 30% (51/166) of E. coli ESBL producers in our hospital. 29 isolates were genotyped by ERIC-PCR and analysed for the SHV-, TEM-, CTX-M-type ESBL genes. Nine different clonal lineages were evidenced and two slightly prevalent clones were identified. The most diffused ESBL was CTX-M-15, being detected in 27/29 E. coli strains of different genotypes. The two strains lacking the CTX-M-15 were SHV-12 producers. Three strains carried both the SHV-11 and CTX-M-15. Most of the strains were also positive for the blaTEM gene (22/29). The blaCTX-M-15 was detected on similar plasmids in all selected isolates and their transconjugants, belonging to the FII incompatibility group. Further plasmid characterisation is under way.

Conclusion: The eruptive worldwide dissemination of the CTX-M-15 in geographically distinct hospitals emphasizes the necessity of immediate intervention and epidemiological monitoring. E. coli with CTX-M-15 are a major problem in the our hospital causing outbreak as well as many sporadic infections. The impressive prevalence of this genetic trait in our hospital seems associated to the diffusion of epidemic plasmids and the current knowledge on the spread of these plasmids is still limited but it should be taken into account for the design of control measures.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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