The Emerging Resistance Index: tracking early resistance to new antibiotics

A new study introduces the Emerging Resistance Index (ERI) — a quantitative tool designed to monitor how quickly resistance develops to newly approved antibiotics. The ERI integrates multiple parameters, including pooled AMR proportions and trends, the presence of resistance and antibiotic use surveillance systems, the time between drug approval and resistance detection, and the frequency of resistance-related outbreaks. Using data from 38 European surveillance systems covering 13 recently approved antibiotics, the analysis showed rapid resistance emergence for all new Gram-negative-targeting drugs, especially imipenem–relebactam and cefiderocol. Combinations of older β-lactams with new inhibitors were particularly vulnerable to resistance. The ERI offers a promising dynamic framework to track resistance evolution, guide surveillance and policy decisions, and help prioritize future antibiotic research and development.