Fosfomycin Susceptibility Testing Using Commercial Agar Dilution Test

Peter D Croughs, Michelle Konijnendijk-de Regt, Erlangga Yusuf*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

2 Citations (Scopus)
34 Downloads (Pure)


The reference standard for fosfomycin antimicrobial susceptibility testing (AST) is agar dilution, but it is laborious and is not routinely used in diagnostic microbiology. In this study, we evaluated the performance of a ready-to-use commercially available agar dilution kit for fosfomycin AST (Liofilchem Diagnostics). We compared this kit with the reference standard agar dilution, performed according to the Clinical & Laboratory Standards Institute (CLSI) in 229 clinical isolates. The isolates were selected to represent both Gram-positive and Gram-negative microorganisms, with various MIC values. It consisted of 43 enterococci (E. faecalis n = 16, E. faecium n = 27), 13 methicillin-resistant S. aureus (MRSA), 118 Enterobacterales (Escherichia coli n = 94, Klebsiella pneumoniae n = 20, and Enterobacter cloacae complex n = 4), 55 Pseudomonas aeruginosa, and three ATCC isolates. Using CLSI breakpoints for enterococci for oral treatment of urinary tract infections, European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints for intravenous dosing for Enterobacterales and Staphylococci, and epidemiological cutoff value for P. aeruginosa, the essential agreement was 87.5%, and 99.6% after discrepancy resolution. There was no very major error, and 1.9% major error before, and 0.9% major error after resolution of discrepancies. The commercial test showed 100% reproducibility. In conclusion, in comparison to the reference standard, the ready-to-use commercially available agar dilution kit for fosfomycin AST showed excellent performance.

Original languageEnglish
Pages (from-to)e0250421
JournalMicrobiology spectrum
Issue number2
Early online date30 Mar 2022
Publication statusPublished - 27 Apr 2022

Bibliographical note

Publisher Copyright:
Copyright © 2022 Croughs et al.


Dive into the research topics of 'Fosfomycin Susceptibility Testing Using Commercial Agar Dilution Test'. Together they form a unique fingerprint.

Cite this