Table 6.
A comparison of the expected and observed result, colour of colonies and sensitivity
| ChromID ESBL | Brilliance ESBL | Drigalski (BLSE agar) | MacConkey (BLSE agar) | CHROMagar ESBL | |
|---|---|---|---|---|---|
| Observed /Expected ESBL A -positive | 51/51 | 51/51 | 50/51 | 50/51 | 51/51 |
| Observed/Expected AmpC-positive | 32/36 | 31/0 | 36/36 | 36/36 | 23/0 |
| Expected colour of colonies | Colourless | Colourless | Blue | White | Colourless |
| Colour of Salmonella colonies | Colourless (n = 62) Pink (n = 3) | Colourless (n = 61) Pink (n = 3) | Blue | Pale pink | Colourless |
| Colour of Shigella sonnei colonies | Pink | Blue | Blue | Pale pink | Pink |
| Colour of Shigella flexneri colonies | Colourless | Colourless | Blue | Pale pink | Colourless |
| Sensitivity (95% CI*) | 95% (90.4 - 99.6) | 93% (87.6 - 98.4) | 99% (96.9 - 100) | 99% (96.9 - 100) | 85% (77.5 - 92.5) |
| Sensitivity ESBL A (95% CI*) | 100% | 100% | 98% (94.2 - 100) | 98% (94.2 - 100) | 100% |
| Sensitivity AmpC (95% CI*) | 89% (78.8 - 99.2) | 83% (70.7 - 95.3) | 100% | 100% | 64% (48.3 - 79.7) |
A total of 87 ESBL-producing isolates (51 = ESBLA, 36 = AmpC) were inoculated on the four screening agars. BLSE agar is a biplate consisting of two different agars; Drigalski agar and MacConkey agar. The isolates were mixed with a fecal suspension before inoculation. The expected results are estimated by the manufacturer’s product information.
*CI = 95% Confidence interval.