TABLE 1.
Agar dilution and Etest fosfomycin MICsg
| Pathogen (no. of isolates) and MIC test method | MIC (μg/ml) |
MIC interpretationa (%) |
Test method agreement and error rates (%) |
||||||
|---|---|---|---|---|---|---|---|---|---|
| MIC50 | MIC90 | Range | Susceptible | Resistant | EAb (n) | CAc (n) | MEd (n) | VMEe (n) | |
| Enterobacterales (199) | |||||||||
| Agar dilution | 16 | 512 | ≤1–>512 | 73.4 | 26.6 | ||||
| Etest | 16 | 512 | ≤1–>512 | 78.9 | 21.1 | 70.4 (126/179) | 88.4 (176/199) | 4.1 (6/146) | 32.1 (17/53) |
| Enterobacter cloacae (32) | |||||||||
| Agar dilution | 16 | 128 | ≤1–512 | 65.6 | 34.4 | ||||
| Etest | 32 | 512 | ≤1–>512 | 62.5 | 37.5 | 71.4 (20/28) | 84.4 (27/32) | 14.3 (3/21) | 18.2 (2/11) |
| Klebsiella aerogenes (21) | |||||||||
| Agar dilution | 16 | 64 | 1–512 | 81.0 | 19.0 | ||||
| Etest | 16 | 32 | ≤1–>512 | 90.5 | 9.5 | 85.0 (17/20) | 90.5 (19/21) | 0 (0/17) | 50.0 (2/4) |
| Klebsiella oxytoca/Raoultella spp. (30) | |||||||||
| Agar dilution | 16 | 32 | 2–256 | 93.3 | 6.7 | ||||
| Etest | 8 | 16 | ≤1–64 | 96.7 | 3.3 | 56.7 (17/30) | 96.7 (29/30) | 0 (0/28) | 50.0 (1/2) |
| Klebsiella pneumoniae (51) | |||||||||
| Agar dilution | 32 | 128 | 16–>512 | 68.6 | 31.4 | ||||
| Etest | 16 | 64 | 4–>512 | 88.2 | 11.8 | 60.0 (30/50) | 72.5 (37/51) | 5.7 (2/35) | 75.0 (12/16) |
| Morganella morganii (15) | |||||||||
| Agar dilution | 512 | >512 | 128–>512 | 0 | 100 | ||||
| Etest | >512 | >512 | 256–>512 | 0 | 100 | 25.0 (1/4) | 100 (15/15) | NAf (0/0) | 0 (0/15) |
| Proteus mirabilis (20) | |||||||||
| Agar dilution | 4 | 128 | ≤1–>512 | 75.0 | 25.0 | ||||
| Etest | 2 | 256 | ≤1–>512 | 75.0 | 25.0 | 76.5 (13/17) | 100 (20/20) | 0 (0/15) | 0 (0/5) |
| Serratia marcescens (30) | |||||||||
| Agar dilution | 16 | 16 | 4–32 | 100 | 0 | ||||
| Etest | 16 | 32 | 4–128 | 96.7 | 3.3 | 93.3 (28/30) | 96.7 (29/30) | 3.3 (1/30) | NA (0/0) |
| Acinetobacter baumannii (15) | |||||||||
| Agar dilution | 128 | 256 | 128 −512 | ||||||
| Etest | 256 | >512 | 264–>512 | 64.3 (9/14) | |||||
| Pseudomonas aeruginosa (50) | |||||||||
| Agar dilution | 128 | 256 | 4–>512 | ||||||
| Etest | 128 | >512 | 4–>512 | 77.6 (38/49) | |||||
| Stenotrophomonas maltophilia (25) | |||||||||
| Agar dilution | 128 | 256 | 64 −256 | ||||||
| Etest | >512 | >512 | 64–>512 | 32.0 (8/25) | |||||
EUCAST (4) MIC breakpoints (susceptible, ≤32 μg/ml; resistant, >32 μg/ml) apply to isolates of Enterobacterales and intravenous use of fosfomycin.
EA, essential agreement. The EA calculation excluded one or two indeterminate off-scale MIC readings (e.g., <1 or >512 μg/ml) where a determination of EA could not be made. The number of isolates included in calculation appears in parentheses after the percentage.
CA, categorical agreement. 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 calculation appears in parentheses after the percentage.
NA, not applicable.
Agar dilution and Etest fosfomycin MICs were interpreted by EUCAST fosfomycin intravenous breakpoints for 199 isolates of Enterobacterales other than E. coli and 90 isolates of nonfermenting Gram-negative bacilli.