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

Abstract

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.

• Authors: Rafael Cantón, David M Livermore, María Isabel Morosini, Jazmín Díaz-Regañón, Gian Maria Rossolini, PREMIUM Study Group
• Journal: The Journal of antimicrobial chemotherapy (J Antimicrob Chemother) Vol. 72 Issue 2 Pg. 431-436 (02 2017) ISSN: 1460-2091 [Electronic] England
• PMID: 27798220 (Publication Type: Comparative Study, Evaluation Study, Journal Article, Multicenter Study)
• Copyright: © The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy.

Chemical References

• Anti-Bacterial Agents
• Cephalosporins

Topics

• Adolescent
• Adult
• Aged
• Aged, 80 and over
• Anti-Bacterial Agents (pharmacology)
• Cephalosporins (pharmacology)
• Community-Acquired Infections (microbiology)
• Europe
• Female
• Humans
• Male
• Microbial Sensitivity Tests (methods)
• Middle Aged
• Pneumonia, Staphylococcal (microbiology)
• Staphylococcal Skin Infections (microbiology)
• Staphylococcus aureus (drug effects, isolation & purification)
• Young Adult
• Ceftaroline