Detection of extended-spectrum beta-lactamases among Enterobacteriaceae using automated microbiology systems and manual detection procedures

Abstract number: p988

Seifert  H., Geiss  H.K., Mack  D., Stürenburg  E., Wiegand  I.


The reliability of automated antibiotic susceptibility testing systems for the detection of extended-spectrum beta-lactamases (ESBLs) among Enterobacteriaceae is crucial for optimal patient therapy and outbreak management.


A total of 150 strains, including Escherichia coli (62), Klebsiella spp. (45), Enterobacter spp. (24), Citrobacter spp. (6), Morganella morganii (4), Proteus spp. (7), and Serratia marcescens (1) were tested. Three automated microbiology systems were compared: The Phoenix™ Automated Microbiology System (BD Diagnostic Systems, Sparks, MD), the VITEK® 2 system (bioMérieux, Marcy l'Etoile, France), and the Microscan WalkAway®-96 SI (Dade Behring, Inc.). Conventional phenotypic confirmatory test such as the NCCLS double disk synergy test (DDS), the disk approximation method (DAM), and the Etest ESBL (AB biodisk, Solna, Sweden) were also evaluated. Combined uses of isoelectric focusing, PCR procedures for the detection of TEM and SHV genes, and/or DNA sequencing were used as the reference method.


Of the total 150 isolates, 95 were ESBL producers as determined by the reference methods, 2 isolates were excluded due to indeterminate results, and the remaining 53 isolates were identified as non-ESBL producers. The sensitivity, specificity, negative (NPV) and positive (PPV) predictive values were determined:


These results indicate that the Phoenix System offers the highest sensitivity and acceptable specificity among the automated susceptibility testing systems for the detection of ESBL production in clinically important Enterobacteriaceae. The most reliable overall performance was achieved with the ESBL ETest.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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