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In vitro activity of ertapenem in comparison with imipenem against Enterobacteriaceae in Turkey

Abstract number: P1040

Altinkanat G., Mete B., Ögünç D., Özakin C., Sümerkan B., Ergönül Ö., Söyletir G., Korten V.

Objectives: To evaluate the in vitro activity of ertapenem against E. coli, Klebsiella spp. and Enterobacter spp. in the first year of its launch in Turkey.

Methods: A total of 416 non-duplicate clinical isolates of ESBL positive E. coli, ESBL positive Klebsiella spp. and Enterobacter spp. isolated during 2006 to 2008 from 5 University hospitals were included in the study. Antimicrobial susceptibilities of ertapenem and imipenem were determined by E-test method according to the CLSI breakpoints. ESBL production was confirmed at the coordinating centre by CLSI disk method by using both ceftazidime and cefotaxime with and without clavulanate. A difference of geqslant R: gt-or-equal, slanted 5 mm between the zone diameters of either of the cephalosporin disks and their respective cephalosporin/clavulanate disk is taken to be phenotypic confirmation of ESBL production. Isolates with a carbapenem MIC of geqslant R: gt-or-equal, slantedmg/ml were screened for carbapenemases by the modified Hodge test and PCR for OXA-48, VIM, IMP and KPC genes.

Results: The in vitro activity of ertapenem was as follows (Table 1).

The body sites of infections were bloodstream (34%), urinary tract (34%), skin and soft tissue (11%), lower respiratory tract (8%) and others (13%). MIC50 of ertapenem were lower than imipenem for all species, about two to five fold more active than imipenem. Despite this good activity, the MICs of ertapenem for ESBL-producing Enterobacteriaceae with reduced sensitivity to carbapenems were higher than imipenem. Imipenem was active (MICs <2 mg/L) in 10 of 12 ertapenem non-susceptible isolates. No isolate was imipenem resistant and ertapenem susceptible. The modified Hodge test was positive in 9 of 23 isolates with reduced carbapenem susceptibility. Eight OXA-48 and 1 VIM genes were found in 9 isolates, all of them were the modified Hodge test positive isolates. No IMP or KPC was found.

Conclusion: The susceptibility of ertapenem was 1–2% less than imipenem in ESBL producing Enterobacteriaceae. Isolates with putative carbapenemases were rarely encountered. The rest of the isolates with reduced sensitivity to carbapenems most likely have ESBLs or AmpC enzymes plus impermeability and/or increased efflux.

Table 1. In vitro activities of ertapenem and imipenem against Enterobacteriaceae in Turkey

 MIC50MIC90RangeSusceptibility (%)
E. coli ESBL(+), n = 166    
  Ertapenem0.0640.250.012–2499
  Imipenem0.190.250.125–1.5100
Klebsiella spp. ESBL(+), n = 162    
  Ertapenem0.0940.380.008–3297
  Imipenem0.190.250.125–3299
Enterobacter spp., n = 88    
  Ertapenem0.0470.50.008–3297
  Imipenem0.250.380.125–3299

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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