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Journal of Clinical Microbiology, November 2008, p. 3721-3727, Vol. 46, No. 11
0095-1137/08/$08.00+0     doi:10.1128/JCM.00777-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Extended-Spectrum Beta-Lactamase Detection with Different Panels for Automated Susceptibility Testing and with a Chromogenic Medium{triangledown}

J. Färber,{dagger}* K.-A. Moder,{dagger}* F. Layer, I. Tammer, W. König, and B. König

Institute of Medical Microbiology, Otto-von-Guericke University Magdeburg, Leipziger Str. 44, 39120 Magdeburg, Germany

Received 24 April 2008/ Returned for modification 16 June 2008/ Accepted 13 September 2008

Infections caused by extended-spectrum beta-lactamase (ESBL)- and ampC beta-lactamase-producing gram-negative bacteria complicate therapy and limit treatment options. Several different panels for ESBL detection with automated systems exist. In addition, a chromogenic agar medium is available for ESBL screening. We compared two automated identification and susceptibility testing systems with regard to their effectiveness in detecting ESBL production in Enterobacteriaceae: the BD Phoenix system (BD Diagnostic Systems, Sparks, MD) and the Vitek 2 system (bioMerieux, Marcy l'Etoile, France). We tested 114 strains using the Etest as the standard, various available panels for both automated systems (for BD Phoenix, the NMIC/ID-50 and NMIC/ID-70 GN Combo panels for combined identification and susceptibility testing of gram-negative bacilli, and for Vitek 2, the ID-GNB panel for identification of gram-negative bacilli and the AST-N020, AST-N041, and AST-N062 panels for susceptibility testing), and a chromogenic agar medium (bioMérieux, Marcy l'Etoile, France). PCR for common ESBL gene families (encoding TEM, SHV, OXA, and CTX-M) and for chromosomal or plasmid-mediated ampC beta-lactamase genes was conducted to complete the study design. For the tested specimens overall, the chromID ESBL agar showed the highest sensitivity (95.8%) but the lowest specificity (10.5%) compared to the sensitivity and specificity of the Etest (chosen as reference by the authors) for the detection of ESBL-producing strains. The BD Phoenix system showed sensitivities of 77.1% and 84.2% and specificities of 61.5% and 75.0%, respectively, for the NMIC/ID-50 andNMIC/ID-70 panels. The sensitivity of the Vitek 2 system ranged from 78.8% (AST-N020) to 80.6% (AST-N062) and up to 84.2% (AST-N041). The specificities of the respective panels were 50.0% (AST-N041 and AST-N062) and 55.6% (AST-N020). In conclusion, the sensitivities and specificities of ESBL detection by the different methods differ depending on the microorganisms under study.

* Corresponding author. Mailing address: Institute of Medical Microbiology, Otto-von-Guericke University Magdeburg, Leipziger Str. 44, 39120 Magdeburg, Germany. Phone: 49-391-6713393. Fax: 49-391-6713384. E-mail for J. Färber: jacqueline.faerber{at}med.ovgu.de. E-mail for K.-A. Moder: karen.moder{at}med.ovgu.de

{triangledown} Published ahead of print on 24 September 2008.

{dagger} Both authors contributed equally to this work.

Journal of Clinical Microbiology, November 2008, p. 3721-3727, Vol. 46, No. 11
0095-1137/08/$08.00+0     doi:10.1128/JCM.00777-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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