Impact of a real-time diagnostic and antimicrobial stewardship workflow on time to appropriate therapy for infections caused by multidrug-resistant Gram-negative organisms.

Introduction: Multidrug-resistant (MDR) Gram-negative organisms cause life-threatening infections, and the incidence is rising globally. Timely therapy for these infections has a direct impact on patient survival. This study aimed to determine the impact of a multidisciplinary diagnostic and antimicrobial stewardship (AMS) workflow on time to appropriate therapy (TAP) for these infections using novel beta-lactam/beta-lactamase inhibitors.

Methods: This was a retrospective quasi-experimental study of adult patients with carbapenem-resistant Enterobacterales (CRE) and multidrug-resistant Pseudomonas (MDR PsA) infections at a 1500 bed university hospital. Included patients who received ≥ 72 hours of ceftazidime-avibactam (CZA) or ceftolozane-tazobactam (C/T) from December 2017 to December 2019. During the pre-intervention period (December 2017 to December 2018), additional susceptibilities (including CZA and C/T) were performed only upon providers' request. In 2019, reflex algorithms were implemented for faster identification and testing of all CRE/MDR PsA isolates. Results were communicated in real-time to the AMS team to tailor therapy.

Results: A total of 99 patients were included, with no between-group differences at baseline. The median age was 60 years and 56 (56.7%) were in intensive care at the time of culture collection. Identified organisms included 71 (71.7%) MDR PsA and 26 CRE, of which 18 were carbapenemase producers (Klebsiella-producing carbapenemase = 12, New Delhi metallo-β-lactamase = 4, Verona integron-encoded metallo-β-lactamase = 2). The most common infections were pneumonia (49.5%) and bacteraemia (30.3%). A decrease was found in median TAP (103 [IQR 76.0-156.0] vs. 75 [IQR 56-100] hours; P < 0.001). Median time from culture collection to final susceptibility results was shorter in the post-intervention group (123 vs. 93 hours; P < 0.001).

Conclusion: This study identified improvement in TAP in MDR PsA and CRE infections with implementation of a reflex microbiology workflow and multidisciplinary antimicrobial stewardship initiatives.