title: Fosfomycin susceptibility in carbapenem-resistant Enterobacteriaceae from Germany.
abstract: Due to the increase in multidrug-resistant Enterobacteriaceae, the interest in older antimicrobial agents, like fosfomycin, has increased. In this study, we used agar dilution for testing susceptibilities to fosfomycin in a collection of 107 carbapenem-nonsusceptible Enterobacteriaceae isolates, of which 80 produced various types of carbapenemases, including KPC, VIM, NDM, and OXA-48. Overall, 78% of the strains had fosfomycin MICs of ≤ 32 mg/liter and were thus considered to be susceptible according to the current EUCAST breakpoint. The MIC50 and MIC90 were 8 mg/liter and 512 mg/liter, respectively. Escherichia coli strains had significantly lower fosfomycin MICs than the Klebsiella pneumoniae and Enterobacter cloacae strains. Furthermore, comparisons of the susceptibility testing methods, like Etest and disk diffusion, were performed against agar dilution as the reference method. Essential agreement between Etest and agar dilution was 78.9%, and categorical agreement between the two methods was 92.5%, with 20% very major errors and 2.6% major errors. Disk diffusion was studied with 50-μg and 200-μg fosfomycin disks, but no inhibition zone breakpoint that reduced very major and major errors to an acceptable level was found. Etest and disk diffusion showed poor agreement with fosfomycin agar dilution.
authors.affiliation: Department of Medical Microbiology, Ruhr-University Bochum, Bochum, Germany martin.kaase@rub.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Kaase
authors.affiliation: Laborarztpraxis Osnabrück, Georgsmarienhütte, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Szabados
authors.affiliation: Department of Medical Microbiology, Ruhr-University Bochum, Bochum, Germany.
authors.forename: Agnes
authors.initials: A
authors.lastname: Anders
authors.affiliation: Department of Medical Microbiology, Ruhr-University Bochum, Bochum, Germany.
authors.forename: Sören G
authors.initials: SG
authors.lastname: Gatermann
mesh_terms: D015780:Carbapenems / Q000494:pharmacology*; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000382:microbiology*; D005578:Fosfomycin / Q000494:pharmacology*; D005858:Germany; D006801:Humans; D008826:Microbial Sensitivity Tests; D018440:beta-Lactam Resistance
chemical_list: D015780:Carbapenems; D005578:Fosfomycin