VIM-1 and CTX-M-9 in E. cloacae, K. pneumoniae and K. oxytoca clinical strains

Abstract number: P2082

Miró E., Segura C., Navarro F., Horcajada J., Sorli L., Alvarez F., Salvadó M.

Objectives: The carbapenem-hydrolysis b-lactamases (CHBL) begins to be clinically relevant. This resistance poses two major challenges, detection in the microbiology laboratory and the choice of a valid antibiotic therapy.

We describe 12 Enterobacteriaceae isolates with carbapenemase activity isolated at Hospital del Mar (Barcelona, Spain) from December 2006 to May 2007. Two of them also produced the CTX-M-9 ESBL.

Methods: Identification and susceptibility of isolates were done by MicroScan system (Urine ComboS1 and NC36 panels). To confirm carbapenem resistance, imipenem and ertapenem disc diffusion, imipenem and imipenem+EDTA E-test and the cloverleaf test were performed. PFGE using XbaI restriction enzyme was done to disregard clonality between the different isolates. The b-lactamases genes were characterised by PCR and sequencing. The incompatibility group of the CHBL carrying plasmid was determined by incompatibility group determination, and was made by rep-typing PCR, S1 digestion, PFGE, Southern Blot and hybridisation with specific probes for 18 different incompatibility groups.

Results: Seven Enterobacter cloacae, 2 Klebsiella pneumoniae and 3 Klebsiella oxytoca isolates showed a VIM-1 metallo-b-lactamase. Four clones were found among the E. cloacae isolates: PFGE-I with 3 strains, PFGE-II with two strains and PFGE-III and IV with one isolate each. The three K. oxytoca strains were clonal. The 3 E. cloacae with PFGE pattern I and three K. oxytoca strains also presented the CTX-M-9 enzyme. Two plasmids of 38 bp and 75 bp hybridised with the carbapenem resistance probe, but we were unable to define the incompatibility group. The blaCTX-M-9 was found in a HI2 plasmid of 290 pb.

All isolates were classified as susceptible by MicroScan system; only two E. cloacae had slightly higher MICs values (IMP 4 mg/ml and ERT 2 mg/ml). The disc diffusion method correctly classified E. cloacae isolates as intermediate or resistant but were not the case for Klebsiella isolates. A slight synergy effect was observed with EDTA in the E-test. The cloverleaf test was positive in all isolates, but not proved useful in E. cloacae due to the interference with his chromosomal betalactamase.

Conclusions: It is important for laboratories to be aware of carbapenem resistance detection because is elusive in some cases. Additional tests like disk diffusion, E-test, cloverleaves are mandatory when treatment relies on these antibiotics.

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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