The Impact of Pharmacist-Led Antimicrobial Stewardship Review of Cultures in the Ambulatory Setting at a Comprehensive Cancer Center

Background: Several antimicrobial stewardship interventions have demonstrated improved clinical outcomes. Though the impact of a pharmacist-led antimicrobial stewardship review of cultures has been described, studies have not evaluated such an intervention in institutions that primarily serve cancer patients. Aim: To describe the impact of the antimicrobial stewardship pharmacist's review of microbiological cultures from adult cancer patients in the ambulatory setting. Method: A retrospective study at a comprehensive cancer center that included adult cancer patients with positive microbiological cultures treated in the ambulatory setting, between August 2020 and February 2021. The cultures were reviewed in real time by the antimicrobial stewardship pharmacist, and were assessed for appropriateness of treatment. The number of antimicrobial modifications made, type of modifications, and physicians' acceptance rate were recorded. Results: A total of 661 cultures from 504 patients were reviewed by the pharmacist. The mean age of patients was 58 years +/- 16 (SD); most had solid tumors (95%), and 34% were recent recipients of chemotherapy. Among the reviewed cultures, 175 (26%) required antimicrobial therapy modification, with an acceptance rate of 86%. The modifications consisted of changing from non-susceptible to susceptible antimicrobials (n = 95, 54%), initiation (n = 61, 35%), discontinuation (n = 10, 6%), de-escalation (n = 7, 4%), and dose modification (n = 2, 1%) of antimicrobials. Conclusion: Around one fourth of the cultures reviewed by the antimicrobial stewardship pharmacist in the ambulatory setting required interventions to optimize therapy. Future studies should evaluate the impact of these interventions on clinical outcomes.