TABLE 4.
Distribution of the results of different disk diffusion techniques
| Test and drug | Test result | Category (no. of isolates)
|
Sensitivity | Specificity | |
|---|---|---|---|---|---|
| ESBL | Non-ESBL | ||||
| CLSI ESBL initial screena | |||||
| Ceftazidime | Positive | 14 | 9 | 0.93 | 0.70 |
| Negative | 1 | 21 | |||
| Cefotaxime | Positive | 14 | 9 | 0.93 | 0.70 |
| Negative | 1 | 21 | |||
| CLSI ESBL phenotypic confirmatory testb | |||||
| Ceftazidime | Positive | 7 | 0 | 0.47 | 1 |
| Negative | 8 | 30 | |||
| Cefotaxime | Positive | 5 | 0 | 0.33 | 1 |
| Negative | 10 | 30 | |||
| Double disk diffusion test (20 mm) | |||||
| Ceftazidime | Positive | 6 | 0 | 0.40 | 1 |
| Negative | 9 | 30 | |||
| Cefotaxime | Positive | 7 | 0 | 0.47 | 1 |
| Negative | 8 | 30 | |||
| Double disk diffusion test (30 mm) | |||||
| Ceftazidime | Positive | 1 | 0 | 0.07 | 1 |
| Negative | 14 | 30 | |||
| Cefotaxime | Positive | 7 | 0 | 0.47 | 1 |
| Negative | 8 | 30 | |||
a
The CLSI disk inhibition break points for ESBL initial screen of E. coli and Klebsiella spp. were <22 mm for ceftazidime (30 μg) and <27 mm for cefotaxime (30 μg).
b
A >5-mm increase in zone diameter in combination with clavulanic acid versus when tested alone.