Molecular epidemiology and typing of CTX-M extended-spectrum

Abstract number: 1733_70

Xu L., Morris D., Biernacka K., Woodford N., Hawkey P., Nye K.

Objectives: The aims of this study were to investigate the molecular epidemiology of CTX-M Extended-Spectrum B-Lactamase-Producing Enterobacteriaceae in both hospital and community patients in the area served by the Heart of England NHS Foundation Trust, Birmingham.

Methods: Between January and April 2006, a total of 2529 consecutive non-duplicate isolates of Enterobacteriaceae were processed by the clinical service. All isolates were screened for susceptibility to cefpodoxime by the BSAC disc diffusion method and ESBL production confirmed using cefpodoxime, cefpirome and ceftazidime with and without clavulanate. Multiplex PCR was used to detect all blaCTX-M genes. The blaCTX-M positive isolates were characterised by dHPLC and results further confirmed by DNA sequencing. Clonal relatedness was identified by PFGE analysis.

Results: A total of 82 isolates (3.2%) were confirmed to produce ESBL, including 53 isolates (64.6%) from hospital and 29 isolates (35.4%) from the community. These isolates included 64 E. coli, 15 Klebsiella spp., 2 E. cloacae and 1 Citrobacter freundii. Multiplex PCR screening identified a blaCTX-M gene in 76 isolates (92.7%). Multiplex PCR screening identified a blaCTX-M gene in 76 isolates. Of these, 71 belonged to a blaCTX-M group 1, and 5 harboured a blaCTX-M group 9 gene. The dHPLC genotyping of group 1 isolates showed that all had blaCTX-M-15 profiles. The 5 group 9 isolates depicted a blaCTX-M-14 chromatogram signature. DNA sequencing confirmed blaCTX-M-15 in 8 representative strains of the 71 dHPLC typed CTX-M-15 isolates and all 5 blaCTX-M-14 producers. PFGE analysis showed the 60 blaCTX-M positive E. coli isolates to represent multiple strains among which 7 clusters of 2 or more isolates and 16 distinct strains (>85% similarity) were observed, eight were strain A.

Conclusion: This study confirms that blactx-m-15 is the commonest cause of ESBL production in this locality. blaCTX-M-14 accounted for 6.6% of all our CTX-M producing isolates, which has not formally reported as causing disease in the UK, it may displace blaCTX-M-15. There was evidence of dissemination of clonally related isolates among patients both in the hospital and the community. Strain A has been reported to comprise 38% UK isolates, but only 13% in our study.

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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