Table 3.
Distribution of discrepancies in MIC values of 21 antimicrobials and categorical error rates for Staphylococcus spp.
| Antimicrobial | No. of MICs reported (no. of centres)a |
Discrepant MICs (%)b | No. of MICs interpreted using |
Categorical errors (%)c |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Overall |
mEs |
MEs |
VMEs |
|||||||||
| EUCAST | CLSI | EUCAST | CLSI | EUCAST | CLSI | EUCAST | CLSI | EUCAST | CLSI | |||
| Daptomycin | 329 (49) | 21.3 | 223 | 106 | 1.7 | 0.0 | 0.0 | 0.0 | 0.4 | 0.0 | 1.3 | 0.0 |
| Oxacillin | 374 (50) | 20.6 | 258 | 116 | 6.6 | 3.4 | 0.4 | 0.0 | 1.9 | 3.4 | 4.3 | 0.0 |
| Fosfomycin | 27 (6) | 18.6 | 14 | 13 | 14.3 | NA | 0.0 | NA | 14.3 | NA | 0.0 | NA |
| Clindamycin | 355 (51) | 13.5 | 243 | 112 | 3.2 | 4.5 | 0.4 | 0.9 | 1.2 | 0.0 | 1.6 | 3.6 |
| Penicillin G | 293 (44) | 13.3 | 192 | 101 | 1.0 | 0.0 | 0.5 | 0.0 | 0.0 | 0.0 | 0.5 | 0.0 |
| Vancomycin | 364 (49) | 9.1 | 248 | 116 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Tobramycin | 246 (35) | 8.9 | 187 | 59 | 9.6 | NA | 0.0 | NA | 9.1 | NA | 0.5 | NA |
| Erythromycin | 357 (51) | 8.4 | 248 | 109 | 2.4 | 7.3 | 1.2 | 7.3 | 0.4 | 0.0 | 0.8 | 0.0 |
| Quinupristin/ dalfopristin | 37 (7) | 8.1 | 19 | 18 | 5.3 | 16.7 | 5.3 | 0.0 | 0.0 | 11.1 | 0.0 | 5.6 |
| Gentamicin | 341 (46) | 7.6 | 244 | 97 | 5.7 | 2.1 | 0.0 | 2.1 | 5.7 | 0.0 | 0.0 | 0.0 |
| Amikacin | 99 (20) | 7.1 | 84 | 15 | 25.0 | NA | 22.6 | NA | 2.4 | NA | 0.0 | NA |
| Linezolid | 370 (51) | 7.0 | 256 | 114 | 5.1 | 4.4 | 0.0 | 0.0 | 0.4 | 0.9 | 4.7 | 3.5 |
| Fusidic acid | 155 (26) | 5.8 | 104 | 51 | 1.0 | NA | 0.0 | NA | 0.0 | NA | 1.0 | NA |
| Co-trimoxazole | 305 (43) | 5.6 | 203 | 102 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Levofloxacin | 292 (44) | 4.1 | 219 | 73 | 1.4 | 4.1 | 0.0 | 1.4 | 0.9 | 2.7 | 0.5 | 0.0 |
| Rifampicin | 232 (36) | 4.3 | 140 | 92 | 1.4 | 3.3 | 0.0 | 2.2 | 1.4 | 1.1 | 0.0 | 0.0 |
| Tetracycline | 144 (25) | 4.9 | 111 | 33 | 4.5 | 3.0 | 1.8 | 0.0 | 0.9 | 0.0 | 1.8 | 3.0 |
| Cefoxitin | 172 (31) | 2.9 | 137 | 35 | 1.5 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 1.5 | 0.0 |
| Teicoplanin | 322 (46) | 1.9 | 224 | 98 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Ciprofloxacin | 213 (29) | 0.9 | 143 | 70 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Chloramphenicol | 48 (9) | 0.0 | 35 | 13 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Overall (%) | 5075 | 10.5 | 3532 | 1543 | 3.8 | 2.3 | 0.8 | 1.0 | 1.8 | 0.7 | 1.2 | 0.6 |
NA, not available.
Number of MIC determinations reported for each AST system. The number of laboratories reporting MICs for each AST system is indicated in parentheses. The 21 antimicrobials were not tested by all five AST methods. Thirteen out of the 33 laboratories using MicroScan and 10 out of the 17 laboratories using VITEK 2 reported the MICs of some antimicrobials, particularly vancomycin, linezolid or daptomycin, using gradient strips.
Percentages of discrepancies in the MICs. MICs >1 dilution from the reference values were considered discrepant. MIC discrepancies >10% are highlighted in bold.
The highest percentages of overall errors, as well as mEs >10%, MEs >3% and VMEs >1.5%, are highlighted in bold.