Access and excess as interacting drivers of antimicrobial resistance in low and middle income countries

Antimicrobial resistance (AMR) disproportionately affects low- and middle-income countries (LMICs). However, dominant stewardship frameworks often emphasize overuse, underrecognizing the access–excess dynamic: inadequate access to effective antimicrobials coexisting with inappropriate use, both potentially contributing to resistance in structurally constrained health systems globally. This review synthesizes health system and socioeconomic determinants of antimicrobial misuse in LMICs, examines pathways through which access deficits and excess use may contribute to AMR, and proposes an integrated systems-level framework to inform context-appropriate stewardship strategies across settings globally. A narrative review with structured search elements was conducted using literature (2010–2026) from databases including PubMed, Scopus, and WHO IRIS. Evidence was analyzed via thematic synthesis and conceptual mapping across relevant domains and system determinants. AMR in LMICs is shaped through two interacting pathways. The access-deficit pathway, driven by poverty and diagnostic limitations, can lead to delayed treatment and subtherapeutic exposure. The excess-use pathway, driven by unregulated markets and informal dispensing, can result in inappropriate exposure. These pathways may converge through selection pressure and horizontal gene transfer. A conceptual U-shaped model proposes that insufficient and excessive exposure may increase AMR risk, with many LMIC settings experiencing conditions at both ends of the exposure spectrum. The Access–Excess–Resistance Pathway Model links health system determinants to resistance outcomes. Effective mitigation in LMICs requires transitioning from restrictive to supportive stewardship, integrating equitable access and system strengthening as interdependent components within a One Health framework.