TABLE 5.
Inter- and intralaboratory comparisons of cefepime-enmetazobactam MICs (enmetazobactam concentration fixed at 8 μg/ml) and inhibition zone diameters with 30/20-μg disks for K. pneumoniae ATCC 700603 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) | ||||||||||||||
| 0.12 | 10 | 3 | 4 | 12 | 2 | 1 | 2 | 17 | ||||||
| 0.25 | 62 | 68 | 69 | 17 | 23 | 27 | 26 | 27 | 24 | 27 | 28 | 199 | ||
| 0.5 | 8 | 9 | 7 | 1 | 7 | 1 | 4 | 3 | 5 | 3 | 24 | |||
| IZD (mm) | ||||||||||||||
| 23 | 1 | 1 | 1 | 1 | ||||||||||
| 24 | ||||||||||||||
| 25 | ||||||||||||||
| 26 | 1 | 4 | 1 | 5 | 1 | 6 | 6 | |||||||
| 27 | 8 | 19 | 4 | 18 | 13 | 14 | 7 | 6 | 4 | 31 | ||||
| 28 | 36 | 53 | 31 | 57 | 63 | 26 | 35 | 12 | 21 | 8 | 1 | 17 | 120 | |
| 29 | 46 | 39 | 46 | 66 | 65 | 12 | 18 | 20 | 10 | 22 | 23 | 9 | 17 | 131 |
| 30 | 37 | 32 | 41 | 51 | 59 | 2 | 22 | 25 | 10 | 15 | 16 | 20 | 110 | |
| 31 | 17 | 9 | 26 | 28 | 24 | 6 | 16 | 1 | 14 | 15 | 52 | |||
| 32 | 12 | 4 | 6 | 11 | 11 | 9 | 12 | 1 | 22 | |||||
| 33 | 2 | 5 | 4 | 3 | 7 | 7 | ||||||||
| 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 | 0.26/30.4 | 0.27/29.8 | 0.27/30.4 | 30.3 | 30.2 | 0.19/27.8 | 0.29/28.2 | 0.24/29.4 | 0.27/30.4 | 0.27/28.7 | 0.27/29.6 | 0.27/30.8 | 0.24/28.9 | 0.26/29.2 |
| Median | 0.25/31 | 0.25/30 | 0.25/30.5 | 30 | 30 | 0.25/28 | 0.25/28 | 0.25/29 | 0.25/30 | 0.25/29 | 0.25/29 | 0.25/31 | 0.25/29 | 0.25/29 |
| Mode | 0.25/31 | 0.25/29 | 0.25/31 | 30 | 31 | 0.25/28 | 0.25/28 | 0.25/30 | 0.25/30 | 0.25/29 | 0.25/29 | 0.25/30 | 0.25/30 | 0.25/29 |
| Geometric mean | 0.24/30.4 | 0.25/29.8 | 0.26/30.4 | 30.2 | 30.2 | 0.19/27.8 | 0.29/28.2 | 0.24/29.4 | 0.27/30.4 | 0.27/28.6 | 0.27/29.6 | 0.27/30.8 | 0.24/28.8 | 0.25/29.2 |
| Range | 3/7 | 3/6 | 3/7 | 7 | 7 | 3/5 | 2/3 | 3/4 | 2/4 | 2/5 | 3/4 | 2/6 | 2/10 | 3/11 |
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 laboratories participated in both broth microdilution MIC and disk diffusion M23 QC studies.