Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5666807 | International Journal of Antimicrobial Agents | 2017 | 4 Pages |
â¢The combination disk diffusion ESBL confirmation test (CDT) is used to confirm ESBL production in Enterobacteriaceae.â¢Concordance between 10-h and 18-h readings of the CDT is high.â¢No change in the testing algorithm is needed.â¢Turnaround time can be significantly reduced by early disk zone reading.
The combination disk diffusion extended-spectrum β-lactamase (ESBL) confirmation test (CDT) is used for the confirmation of ESBL production in Enterobacteriaceae and usually takes 16-20âh to results. In this study, we searched for the shortest possible incubation time without a reduction in reliability. A total of 125 ESBL screening-positive isolates were subjected to CDT and were molecularly characterised by microarray. Inhibition zones were read every hour over 6-18âh of incubation. Concordance between earlier and 18-h readings was calculated for each hour. Results were validated on 224 isolates during routine clinical practice. For the initial 125 isolates, concordance (Cohen's κ) between the 6-h and 18-h readings was 0.88 [95% confidence interval (CI) 0.78-0.96; Pâ<0.001]. The earliest time point for full concordance with the 18-h reading was 10âh. Validation of the 10-h reading for 224 clinical isolates resulted in a concordance of 0.99 (95% CI 0.98-1.0) between the 10-h and 18-h readings. Overall concordance on all 349 isolates was 0.99 (95% CI 0.97-1.0). Reading after 10âh of incubation has an excellent correlation with results after 18âh of incubation. This can significantly reduce the turnaround time for ESBL detection in laboratories with long opening hours or providing a 24/7 service. Consequently, there is a potential for implementing infection control measures up to 8âh earlier.