Comparison of VITEK 2 generated extended spectrum b-lactamase phenotypes to double-disc test results in Enterobacteriaceae

Abstract number: P889

Naumiuk L., Rybak B., Brzezinski G., Naumiuk E., Samet A.

Objectives: The aim of the study was to compare results of extended spectrum b-lactamase (ESBL) detection suggested by ESBL phenotypes generated by VITEK 2 (bioMerieux) advanced expert system (AES) to the results of double disk tests (DDT).

Methods: We retrospectively studied AES generated phenotypes suggesting ESBL presence in Enterobacteriaceae and results of DDT routinly performed to confirm the presence ESBL enzyme. Modified DDT was done with cefepime, cefotaxime and amoxicillin+clavulanic acid disks. AES phenotypes which included ESBL alone and/or ESBL together with other b-lactams phenotypes were taken into analysis. Analysis was performed by our laboratory information system – Promic (Antrez).

Results: From May to November 2007 we performed 928 Enterobacteriaceae susceptibility tests using VITEK 2 cards GN021 or GN041. In 140 isolates – among others 46 Enterobacter cloacae, 29 Escherichia coli, 16 Klebsiella pneumoniae, 13 Citrobacter freundii – AES suggested detection of ESBL phenotype although DDT confirmed its presence in only 66 isolates. The highest agreement between the AES and DDT was in E. coli (100%) and Klebsiella spp. (99%). The least correlation was noted in E. cloacae (46 phenotypes/6 confirmed), Morganella morganii (10/1) and Serratia marcescens (10/2). In 64 isolates when AES suggested ESBL phenotype as a sole b-lactams phenotype DDT confirmed ESBL production in 48 of them. In this case agreement between the AES and DDT with regard to species was the same.

Conclusion: VITEK 2 AES proposed phenotypes which suggest ESBL presence do not need confirmation in E. coli and Klebsiella spp. The same phenotypes in chromosonal cephalosporinase producers like Enterobacter, Citrobacter, Serratia and Morganella always need confirmation by another method for example modified DDT.

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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