Reducing carbapenem use for low-risk AmpC-producing Enterobacterales: impact of a microbiology comment-based stewardship initiative
Hasan Hamze, Geneviève Amaral, Calvin Ka-Fung Lo, Ahmad Aloufi, Stephanie May, Marina Simeonova, Jennifer M. Grant, Victor Tsun Ho YuenAbstract
Background:
AmpC B-lactamases cause resistance to broad-spectrum B-lactams with variable expression dependent on bacterial species. Practice remains heterogenous regarding treatment of infections caused by AmpC organisms. This study aimed to assess the impact of a microbiology comment-based stewardship intervention on the definitive treatment of low-risk AmpC-producing Enterobacterales bacteremia.
Methods:
This was a pre- and posttest quality improvement study conducted at Island Health Authority. A stewardship intervention involving amendment of a microbiology report comment regarding inducible resistance was implemented on February 13, 2023. Patients aged 18 and older with blood cultures growing low-risk AmpC-producing organisms were included. The primary end point of proportion of patients receiving ceftriaxone or piperacillin-tazobactam was compared between pre- (June 2021 to February 2023) and postintervention periods (February 2023 to October 2024). Secondary end points included clinical outcomes, ceftriaxone/piperacilin-tazobactam resistance rates, and C. difficile infection.
Results:
A total of 56 patients were included (25 preintervention and 31 postintervention). Definitive ceftriaxone/pipercillin-tazobactam antibiotic therapy was prescribed more frequently postintervention compared to preintervention (45.8% vs 5.0%, P < .001). After adjusting for critical illness, patients in the postintervention group had 17.7-fold higher odds (CI 1.9–162.6) of receiving definitive ceftriaxone or piperacillin-tazobactam (PTZ) compared to the preintervention group. No patients required retreatment for the same organism initially cultured, and neither group had ceftriaxone or PTZ resistance documented within 30 days posttreatment completion.
Conclusion:
The microbiology comment-based antimicrobial stewardship intervention led to increased ceftriaxone and PTZ prescribing for low-risk AmpC-producing Enterobacterales bloodstream infections compared to carbapenems, without affecting patient outcomes and increasing resistance rates.