Extended-spectrum Beta-lactamase detection with different panels for automated susceptibility testing and with a chromogenic medium.
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.
Institute of Medical Microbiology, Otto-von-Guericke University Magdeburg, Leipziger Str. 44, 39120 Magdeburg, Germany. jacqueline.faerber@med.ovgu.de
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D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001431:Bacteriological Techniques / Q000379:methods*; D002863:Chromogenic Compounds / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000235:genetics; D004755:Enterobacteriaceae / Q000201:enzymology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D016133:Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D002863:Chromogenic Compounds; D003470:Culture Media; D004269:DNA, Bacterial; D001618:beta-Lactamases