Warning! Oxacillinase-mediated carbapenem resistance spreading in Enterobacteriaceae

Abstract number: P1517

Yilmaz M., Aybar Bilir Y., Midilli K., Ozaras R., Mert A., Tabak F., Ozturk R.

Introduction: Resistance to expanded-spectrum cephalosporins in Enterobacteriaceae has been reported to be related to the production of Ambler class A extended-spectrum b-lactamases (ESBLs) and chromosomal and plasmid-encoded AmpC cephalosporinases. However, increasing number of reports regarding b-lactamase mediated resistance to carbapenems in Enterobacteriaceae are being published.

Objectives: Between 2002–2006, we identified 21 Enterobacteriaceae strains that are resistant to any of the carbapenems in the infectious diseases and clinical microbiology laboratory of a 1500 bed university hospital. The aim of the study was to identify the resistance mechanism(s) of carbapenems in these strains and to check for clonal dissemination.

Methods: Bacterial strains and and MIC determinations. All the strains (15 Klebsiella pneumoniae, 1 Escherichia coli, 2 Enterobacter cloaceae and 2 Enterobacter aerogenes) were clinical isolates from the Istanbul University, Cerrahpasa Medical Faculty Hospital, Infectious Diseases and Clinical Microbiology Laboratory. The strains were identified with the API 32GN system. Antibiotic susceptibilities and MICs were with disc diffusion assay and E-test.

IEF analysis. Isoelectric focusing (IEF) analysis was performed with an ampholine polyacrylamide gel (pH 3.5 to 9.5).

PCR experiments and DNA sequencing: Using total DNA of each of the strains, PCR amplifications of the blaOXA-48 genes were performed with the primers OXA-48A (5'-TTGGTGGCATCGATTATCGG-3') and OXA-48B (5'-GAGCACTTCTTTTGTGATGGC-3'), giving rise to a 743-bp fragment.

Molecular typing. Molecular characterisation of the strains was done by macrorestriction analysis of genomic DNA with XbaI (New England BioLabs). DNA fragments were separated by pulsed-field gel electrophoresis (PFGE) in a CHEF-DR II system (Bio-Rad). Electrophoresis conditions were pulse times ranging from 5 to 35 s for 24 h at 6 V/cm and 14°C.

Infection control procedures. Patients from whom carbapenem-resistant Enterobacteriaceae was recovered at any site were visited by a member of the infection control team. Colonisation or infection was determined according to the definition of the Centers for Diseases Control and Prevention for nosocomial infections.

Results and Conclusion: All the carbapenem resistant strains isolated produced OXA-48, a class D oxacillinase significant with carbapenem-hydrolysing activity. No relationship was observed among the seven patients hospitalised in different wards.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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