TABLE 4.
EA, CA, and error rates generated by in vitro testing of clinical isolates of Gram-positive cocci against fosfomycin by agar dilution, disk diffusion, and Etest
| Breakpoints used, pathogen, and method comparison | % EAa (n) | % CA (n) | % mEb (n) | % MEc (n) | % VMEd (n) |
|---|---|---|---|---|---|
| CLSI breakpointse | |||||
| Enterococcus faecalis (69) | |||||
| Agar dilution vs disk diffusion | NAf | 85.5 (59/69) | 14.5 (10/69) | 0 (0/61) | 0 (0/2) |
| Agar dilution vs Etest | 98.5 (65/66) | 81.2 (56/69) | 18.8 (13/69) | 0 (0/61) | 0 (0/2) |
| Disk diffusion vs Etest | NA | 84.1 (58/69) | 14.5 (10/69) | 0 (0/59) | 0 (0/4) |
| EUCAST breakpointsg | |||||
| Staphylococcus aureus (156) | |||||
| Agar dilution vs Etest | 84.1 (127/151) | 98.7 (154/156) | NA | 1.3 (2/156) | NA (0/0) |
| MSSA (56) | |||||
| Agar dilution vs Etest | 86.8 (46/53) | 100 (56/56) | NA | 0 (0/56) | NA (0/0) |
| MRSA (100) | |||||
| Agar dilution vs Etest | 82.7 (81/98) | 98.0 (98/100) | NA | 2.0 (2/100) | NA (0/0) |
EA, essential agreement. The EA calculation excluded indeterminate off-scale MIC readings. The number of isolates included in calculation appears in parentheses after the percentage. The EA calculation excluded isolates with agar dilution MICs of ≤1 μg/ml (lowest dilution tested) and >512 μg/ml (highest dilution tested) and Etest MICs of >512 μg/ml.
mE, minor errors. The number of isolates included in calculation appears in parentheses after the percentage.
ME, major errors. The number of isolates included in calculation appears in parentheses after the percentage.
VME, very major errors. The number of isolates included in the calculation appears in parentheses after the percentage.
MIC results were interpreted as susceptible (≤64 μg/ml), intermediate (128 μg/ml), and resistant (≥256 μg/ml) according breakpoints published in the CLSI M100 standard (3) for Escherichia coli and Enterococcus faecalis urinary tract isolates. Zone diameter results were interpreted as susceptible (≥16 mm), intermediate (13 to 15 mm), and resistant (≤12 mm) according breakpoints published in the CLSI M100 standard (3) for Escherichia coli and Enterococcus faecalis urinary tract isolates.
NA, not applicable.
EUCAST MIC breakpoints (≤32 μg/ml [susceptible], >32 μg/ml [resistant] [4]) apply to isolates of Staphylococcus species and intravenous use of fosfomycin.