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

Background: Extended-spectrum β-lactamase (ESBL)-producing Enterobacterales constitute a global burden for hospital infection, and the 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-Esherichia coli Enterobacterales that produce ESBLs (NEcESBL-producing Enterobacterales). The Rapid ESBL NP and NG CTX-M MULTI tests were performed on colonies grown on chromogenic media. The results of polymerase chain reaction and sequencing of ESBL genes were used as the gold standard.

Results: Among 473 analysed swabs, 75 (15.9%) grew NEcESBL-producing Enterobacterales, leading to 89 isolates. Sensitivities of the synergism, Rapid ESBL NP and NG CTX-M MULTI tests were 0.97 [95% confidence interval (CI) 0.88-0.99], 0.81 (95% CI 0.69-0.89) and 0.90 (95% CI 0.80-0.96), respectively. Specificities were 0.92 (95% CI 0.73-0.99), 0.85 (95% CI 0.64-0.95) and 0.96 (95% CI 0.78-1.00), respectively. Considering the 473 rectal swabs, ESBL screening using the synergism, Rapid ESBL NP and NG CTX-M MULTI tests was calculated. Sensitivities were 0.96 (95% CI 0.86-0.99), 0.81 (95% CI 0.68-0.90) and 0.91 (95% CI 0.79-0.97); specificities were 1.00 (95% CI 0.98-1.00), 0.99 (95% CI 0.98-1.00) and 1.00 (95% CI 0.99-1.00); positive predictive values were 0.96 (95% CI 0.86-0.99), 0.94 (95% CI 0.81-0.98) and 1.00 (95% CI 0.91-1.00); and negative predictive values were 1.00 (95% CI 0.98-1.00), 0.98 (95% CI 0.96-0.99) and 0.99 (95% CI 0.97-1.00), respectively. When no NEcESBL-producing Enterobacterales were observed, the mean TAT was 30 h. When NEcESBL-producing Enterobacterales were identified, the mean TATs were 74.7, 38.0 and 36.7 h for the synergism, Rapid ESBL NP and NG CTX-M MULTI tests, respectively.

Conclusion: The two rapid ESBL tests showed good performance and allowed a reduction in TAT for screening protocols to identify patients carrying ESBL-producing Enterobacterales.