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

Lookup NU author(s): Katherine Gould

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Abstract

© The Author 2016. Objectives: To compare the concordance of ceftaroline MIC values by reference broth microdilution (BMD) and Etest (bioMérieux, France) for MSSA and MRSA isolates obtained from PREMIUM (D372SL00001), a European multicentre study. Methods: Ceftaroline MICs were determined by reference BMD and by Etest for 1242 MSSA and MRSA isolates collected between February and May 2012 from adult patients with community-acquired pneumonia or complicated skin and soft tissue infections; 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 5 of 380 MRSA isolates found ceftaroline susceptible in BMD were miscategorized as resistant by Etest. Twenty-one of the 26 isolates with MICs of 2 mg/L by BMD were then retested 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.

Publication metadata

Author(s): Canton R, Livermore DM, Morosini MI, Diaz-Reganon J, Rossolini GM, on behalf of the PREMIUM Study Group

Publication type: Article

Publication status: Published

Journal: Journal of Antimicrobial Chemotherapy

Year: 2017

Volume: 72

Issue: 2

Pages: 431-436

Print publication date: 01/02/2017

Online publication date: 20/10/2016

Acceptance date: 20/09/2016

Date deposited: 30/05/2017

ISSN (print): 0305-7453

ISSN (electronic): 1460-2091

Publisher: Oxford University Press

URL: https://doi.org/10.1093/jac/dkw442

DOI: 10.1093/jac/dkw442

Notes: Kate Gould = member of the PREMIUM Study Group

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