Antimicrobial resistance of extended-spectrum lactamase producing Escherichia coli and Klebsiella pneumoniae strains from north-eastern Romania

Abstract number: P1267

Tuchilus C., Iancu L.S., Copacianu B., Poiata A., Badescu A., Ambarus A., Lapuste C., Buiuc D.

Family Enterobacteriaceae have developed resistance to third- and fourth-generation cephalosporins via production of extended-spectrum b-lactamases (ESBL). The antimicrobial resistance patterns of ESBL-producing organisms and their prevalence may vary between geographic areas.

Objectives: to evaluate the in vitro antimicrobial resistance and the prevalence Escherichia coli and Klebsiella pneumoniae producing ESBL, isolated from hospital and community in 2009, January-October period.

Materials and Methods: We selected 112 strains (from which, 84 strains were identified as E. coli and 28 as K. pneumoniae) among 611 enterobacteria strains, by using disk diffusion method as initial screening for ESBL, according to Clinical and Laboratory Standard Institute (CLSI) guidelines. For selected strains, the ESBL phenotypic confirmation was performed with double disk test and the replacement disk method. The minimum inhibitory concentrations (MICs) for next antimicrobial agents tested: ceftazidime, cefotaxime, ceftriaxone, cefepime, cefpirome, imipenem, meropenem, ertapenem, moxifloxacin, gatifloxacin, levofloxacin, ofloxacin were performed by agar dilution method. Resistance rates were reported using the CLSI breakpoints for the fully susceptible category; moderately susceptible isolates were classified as resistant. K. pneumoniae ATCC 700603 and E. coli ATCC 25922 were used for quality control.

Results: All 112 tested strains (18.3%) were phenotypically confirmed as ESBL producer, when two phenotypic confirmatory tests were used. Resistance rates for ceftazidime, cefotaxime, ceftriaxone and aztreonam among tested strains were very high: 84.5%, 100%, 100% and 96.4% for E. coli and 98.8%, 98.8%, 97.6% and 89.2% for K. pneumoniae, with the MIC90 values >256 mg/l for either antimicrobial tested agent. The MICs for fourth generation cephalosporins ranges from 4 mg/l to 512 mg/l. The MICs for tested quinolones were >2 mg/l for 89.2% strains. Using breakpoint for susceptibility, all isolates were sensitive to ertapenem, imipenem and meropenem.

Conclusions: Results of this study have shown that ESBL producing E. coli and K. pneumoniae strains circulating in Romania are associated with multidrug resistance. In this study, carbapenems demonstrated the highest degree of activity and are the treatment of choice for ESBL producers.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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