Evaluation of the performance of rapid tests for screening carriers of acquired ESBL producers and their impact on the turnaround time.

Summary Background Extended-Spectrum β-lactamase-producing Enterobacterales (ESBL) constitutes a global burden for hospital infection, and identification of carriers by screening patients at risk is recommended by several guidelines. Aim To evaluate the impact of rapid ESBL tests on the turnaround time (TAT) of screening. Methods Rectal swabs were analysed by culture and synergism tests for identification of non-E.coli Enterobacterales producing ESBL (NEcESBL). The Rapid-ESBL-NP and the NG-CTX-M-multi tests were performed on colonies growing on chromogenic media. Results of PCR and sequencing of ESBL genes were used as gold standard. Results Among 473 analysed swabs, 75 (15.9%) grew NEcESBL, leading to 89 isolates. Sensitivities of the synergism, rapid-ESBL-NP and NG-CTX-M-multi tests were 0.97 (0.88-0.99), 0.81 (0.69-0.89) and 0.90 (0.80-0.96), respectively. Their specificities were 0.92 (0.73-0.99), 0.85 (0.64-0.95) and 0.96 (0.78-1.00), respectively. Considering the 473 rectal swabs, the performance of the procedure for ESBL screening was calculated using the synergism, the rapid-ESBL-NP or the NG-CTX-M-multi tests, respectively. Sensitivities were 0.96 (0.86-0.99), 0.81 (0.68-0.90), 0.91 (0.79-0.97), the specificities 1.00 (0.98-1.00), 0.99 (0.98-1.00) and 1.00 (0.99-1.00), the positive predictive values 0.96 (0.86-0.99), 0.94 (0.81-0.98) and 1.00 (0.91-1.00), the negative predictive values 1.00 (0.98-1.00), 0.98 (0.96-0.99) and 0.99 (0.97-1.00). When no NEcESBL was observed, the mean TAT was 30 hours. When NEcESBL were growing, the means of TAT were 74.7, 38.0 and 36.7 hours using the synergism, the rapid-ESBL-NP or the NG-CTX-M-multi tests, respectively. Conclusion The two rapid ESBL tests showed good performance and allowed the reduction of the TAT of the screening protocol for identification of ESBL carriers.