ESBL evolution in Italy: rapid regional spread of a multidrug-resistant Klebsiella pneumoniae strain producing CTX-M-15

Abstract number: 1733_172

Mugnaioli C., Manso E., Rossolini G.

Objectives: Extended-spectrum b-lactamases (ESBLs) play a crucial role as emerging resistance determinants to expanded-spectrum cephalosporins in Enterobacteriaceae. The CTX-M-type ESBLs have recently undergone a massive spread in several settings, showing a remarkable potential for dissemination. In Italy, we have recently observed a remarkable countrywide dissemination of these enzymes in Escherichia coli (54.8% of ESBL producers) while their prevalence in Klebsiella pneumoniae was found to be much more limited (12.3% of ESBL producers). Here we describe the occurrence of a rapid regional spread of a multidrug resistant (MDR) K. pneumoniae strain producing CTX-M-15.

Methods: susceptibility testing was carried out as recommended by CLSI. Genomic relatedness among the isolates was investigated by RAPD profiling. ESBL determinants were detected by PCR, and the DNA sequence was determined by direct amplicon sequencing. Transfer of resistance genes by conjugation was assayed by mating experiments. Plasmids were characterised by RFLP analysis.

Results: during the period October 2005 – June 2006, 65 consecutive nonreplicate ESBL-positive isolates of K. pneumoniae showing an MDR phenotype including b-lactams (except carbapenems), aminoglycosides and fluoroquinolones were referred to the regional Clinical Microbiology Laboratory of the Marche region (central Italy) from 8 different hospitals. Most isolates were from ICUs, but some were from medical and surgical wards. RAPD analyses revealed clonal relatedness among isolates, all of which were found to carry the blaCTX-M-15 ESBL gene. The gene was carried on a conjugative plasmid that could be efficiently transferred to E. coli (conjugation frequencies in the order of 10-4 transconjugants per recipient). Plasmid analysis revealed apparent identity among CTX-M-15-encoding plasmids from all the isolates.

Conclusion: Results of this study underscore the ability for rapid multifocal spreading of MDR clones of K. pneumoniae that have acquired the CTX-M-15 determinant.

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:
Back to top