Etest® versus broth microdilution for ceftaroline MIC determination with Staphylococcus aureus: results from PREMIUM, a European multicentre study

Cantón, Rafael, Livermore, David M. ORCID:, Morosini, María Isabel, Díaz-Regañón, Jazmín and Rossolini, Gian Maria and The PREMIUM study group (2017) Etest® versus broth microdilution for ceftaroline MIC determination with Staphylococcus aureus: results from PREMIUM, a European multicentre study. Journal of Antimicrobial Chemotherapy, 72 (2). pp. 431-436. ISSN 0305-7453

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Objectives: To compare the concordance of ceftaroline MIC values 24 by reference broth microdilution (BMD) and Etest (BioMérieux, France) for MSSA and MRSA isolates, respectively, in isolates from PREMIUM (D372SL00001), a European multi-centre study.  Methods: Ceftaroline MICs were determined by reference BMD and by Etest for 1,242 MSSA and MRSA from adult patients with community-acquired pneumonia or complicated skin and soft tissue infections collected between February and May 2012; tests were performed across six European laboratories. Selected isolates with ceftaroline resistance in broth (MIC >1 mg/L) were retested in three central laboratories to confirm their behaviour.  Results: Overall concordance between BMD and Etest was good, with >97% essential agreement and >95% categorical agreement. Nevertheless, 12 of the 26 MRSA isolates found resistant by BMD scored as susceptible by Etest, with MICs ≤1 mg/L, thus counting as very major errors, whereas only five of 380 MRSA found ceftaroline susceptible in BMD were mis-categorised as resistant by Etest. Twenty-one of the 26 isolates with MICs of 2 mg/L by BMD were then re-tested twice by each of three central laboratories: BMD MICs of 2 mg/L were consistently found for 19 of the 21 isolates. Among 147 Etest results for these 21 isolates (original plus six repeats per isolate) 112 were >1 mg/L.  Conclusions: BMD and Etest have good overall agreement for ceftaroline against Staphylococcus aureus; nevertheless, reliable Etest-based discrimination of the minority of ceftaroline-resistant (MIC 2 mg/L) MRSA is extremely challenging, requiring careful reading of strips, ideally with duplicate testing.

Item Type: Article
Additional Information: © The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (, which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact Members of the PREMIUM study group are listed in the Acknowledgements section of the paper.
Uncontrolled Keywords: mrsa,ceftaroline,etest,broth microdilution
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User: Pure Connector
Date Deposited: 27 Sep 2016 10:00
Last Modified: 03 Nov 2022 15:40
DOI: 10.1093/jac/dkw442

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