TABLE 6.
Inter- and intralaboratory comparisons of cefepime-enmetazobactam MICs (fixed enmetazobactam concentration of 8 μg/ml) and inhibition zone diameters with 30/20-μg disks for P. aeruginosa ATCC 27853 obtained in the CLSI M23 tier 2 study to establish QC ranges
| Assay measurea | No. of occurrences by medium lotb
|
No. of occurrences by disk lot |
No. of occurrences by laboratoryc
|
Total no. of occurrences | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A | B | C | A | B | A | B | C | D | E | F | G | H | ||
| MIC (μg/ml) | ||||||||||||||
| 0.5 | 3 | 1 | 1 | 2 | 3 | 5 | ||||||||
| 1 | 63 | 68 | 64 | 22 | 25 | 29 | 26 | 20 | 30 | 23 | 20 | 195 | ||
| 2 | 14 | 11 | 14 | 8 | 5 | 1 | 2 | 9 | 7 | 7 | 39 | |||
| 4 | 1 | 1 | 1 | |||||||||||
| IZD (mm) | ||||||||||||||
| 26 | 1 | 2 | 1 | 2 | 3 | |||||||||
| 27 | 8 | 12 | 4 | 13 | 11 | 19 | 2 | 2 | 1 | |||||
| 28 | 32 | 40 | 38 | 55 | 55 | 30 | 29 | 1 | 5 | 20 | 25 | |||
| 29 | 40 | 46 | 44 | 59 | 71 | 8 | 27 | 16 | 7 | 31 | 4 | 9 | 28 | |
| 30 | 52 | 37 | 46 | 68 | 67 | 2 | 39 | 24 | 21 | 20 | 23 | 6 | ||
| 31 | 20 | 21 | 22 | 35 | 28 | 4 | 24 | 1 | 13 | 21 | ||||
| 32 | 5 | 1 | 6 | 7 | 5 | 3 | 3 | 6 | ||||||
| 33 | 2 | 1 | 2 | 1 | 2 | 1 | ||||||||
| Total | 80/160 | 80/160 | 80/160 | 240 | 240 | 30/60 | 30/60 | 30/60 | 30/60 | 30/60 | 30/60 | 30/60 | 30/60 | 240/480 |
| Mean | 1.2/30.4 | 1.1/29.8 | 1.2/30.4 | 29.3 | 29.2 | 1.1/27.8 | 1.1/28.2 | 1/29.4 | 1/30.4 | 1.3/28.7 | 1/29.6 | 1.2/30.8 | 1.1/28.9 | 1.1/29.2 |
| Median | 1/31 | 1/30 | 1/30.5 | 29 | 29 | 1/28 | 1/28 | 1/29 | 1/30 | 1/29 | 1/29 | 1/31 | 1/29 | 1/29 |
| Mode | 1/31 | 1/29 | 1/31 | 30 | 29 | 1/28 | 1/28 | 1/30 | 1/30 | 1/29 | 1/29 | 1/30 | 1/30 | 1/29 |
| Geometric mean | 1.1/30.4 | 1.1/29.8 | 1.1/30.4 | 29.3 | 29.2 | 1.2/27.8 | 1.1/28.2 | 1/29.4 | 1/30.4 | 1.3/28.6 | 1/29.6 | 1.2/30.8 | 1.1/28.8 | 1.1/29.2 |
| Range | 3/8 | 3/8 | 4/6 | 8 | 8 | 2/5 | 2/3 | 2/4 | 3/4 | 3/5 | 1/4 | 2/6 | 3/10 | 4/11 |
Values in bold are results from the broth microdilution MIC assay. Enmetazobactam was included in the combination at a fixed concentration of 8 μg/ml.
The medium used for broth microdilution MIC determinations was cation-adjusted Mueller-Hinton broth from (A) Difco (lot number 5181782), (B) BD (lot number 5257869), and (C) Oxoid (lot number 1433705). The medium used in the disk diffusion assay was Mueller-Hinton agar from (A) Remel (lot number 348358), (B) BBL (lot number 8123531), and (C) Hardy Diagnostics (lot number 417498).
The eight qualified participating laboratories are coded A through H. Only three of the laboratories participated in both broth microdilution MIC and disk diffusion M23 QC studies.