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

• Published in: Journal of Clinical Microbiology 2008-11, Vol.46 (11), p.3721-3727
• Main Authors: Färber, J, Moder, K.-A, Layer, F, Tammer, I, König, W, König, B
• Format: Article
• Language: English
• Subjects: Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriological methods and techniques used in bacteriology; Bacteriological Techniques - methods; Bacteriology; beta-Lactamases - genetics; beta-Lactamases - metabolism; Biological and medical sciences; Chromogenic Compounds - metabolism; Culture Media - chemistry; DNA, Bacterial - genetics; Enterobacteriaceae - enzymology; Fundamental and applied biological sciences. Psychology; Humans; Microbial Sensitivity Tests - methods; Microbiology; Polymerase Chain Reaction - methods; Sensitivity and Specificity
• ISSN: 0095-1137; 1098-660X
• DOI: 10.1128/JCM.00777-08

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.