Robust surveillance metrics are essential to understand how antibiotic use drives antimicrobial resistance (AMR) at the population level.
Longitudinal Norwegian Neisseria gonorrhoeae surveillance data (2003–2024), was used to evaluate ecological AMR metrics and national antibiotic consumption selective pressures. Specifically, the Susceptible Isolate Pressure Indicator ratio (SIPI), was introduced. The SIPI, and wild-type analogue WIPI are mathematical means of describing the changing shape of the MIC distribution histogram in the susceptible range, through time.
Resistance trends correlated with population-level consumption of high-use antibiotic classes, particularly penicillins and tetracyclines, supporting a role for bystander selection and horizontal gene transfer from commensal Neisseria. Traditional surveillance indicators based on resistance prevalence alone were limited in capturing these dynamics within the susceptible MIC zone, particularly under combination therapy regimens. The SIPI ratio enabled detection of antibiotic class-specific selection signals. Notably, SIPI offers a framework to monitor the impact of dual therapy.
As guidelines for administration of the new agents gepotidacin and zoliflodacin are being written to optimise treatment strategies, the SIPI ratio represents an approach for evaluating antimicrobial stewardship that is within reach for all resource settings, to detect early co-resistance associations.