Stewardship in your pocket: launching Colorado's free antimicrobial mobile application.

Objective: The aim was to describe the development and implementation of Firstline (www.Firstline.org), a mobile antimicrobial stewardship (ASP) application (app) created to address barriers to robust ASP in Colorado hospitals. Design: A mixed-methods pragmatic implementation study using the RE-AIM (Reach, Effectiveness, Adoption, Implementation, Maintenance) framework was conducted from October 2023-December 2025. Methods: ASP teams at Children's Hospital Colorado and Denver Health partnered with Firstline to develop the app using locally curated content. The app launched in October 2023 with a multifaceted dissemination campaign. Reach was assessed using geocoded user data. Effectiveness and adoption were evaluated using cross-sectional surveys at two time points. Implementation was characterized by analyzing utilization patterns. Maintenance was assessed by tracking monthly active users over two years. Results: Within the first year, 4,409 unique Colorado users downloaded the app, representing 15% of state clinicians (19% in Denver Metro; 5-17% in rural regions). Survey respondents (n = 215) reported high satisfaction: 63.9% and 72.9% found the app very easy to use, 71.3% and 83.2% reported enhanced antibiotic selection knowledge, and 100% advocated for ongoing support. Among respondents, 10% reported their facilities had formally adopted Firstline guidelines. The most frequently accessed content included common, high-impact infections. Monthly active users remained stable (average 871) over two years. Conclusions: We demonstrated use of Firstline across Colorado, with increasing engagement in rural areas. High user satisfaction, sustained engagement, and emerging institutional adoption suggest this "stewardship in your pocket" model offers a unique, scalable approach to extending ASP support beyond academic medical centers.