Prevalence and patterns of antimicrobial resistance in Escherichia coli from Indonesian broiler chickens: Comparison of CLSI and EUCAST 2025 standards

Abstract

Objectives: This study aimed to compare the prevalence and resistance patterns of antimicrobial resistance (AMR) in Escherichia coli isolated from broiler chickens across Indonesia using the Clinical and Laboratory Standards Institute (CLSI) M100, 35th edition (2025), and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) version 15.0 (2025) guidelines. Material and Methods: A total of 390 E. coli isolates were subjected to antimicrobial susceptibility testing using the broth microdilution method with the Sensititre EUVSEC3 panel. Resistance data were analyzed using the Chi-square test, Cohen’s kappa coefficient, and percent agreement. Results: The highest resistance rates under both standards were observed for ampicillin (78.33% according to CLSI and 78.63% according to EUCAST), while all isolates remained susceptible to meropenem (100%) based on both references. Significant differences between CLSI and EUCAST interpretations were observed for colistin and ciprofloxacin (p < 0.05). Colistin demonstrated negligible agreement between the two standards (κ = –0.01; 95% CI: –0.05 to 0.03; 3% agreement). In contrast, interpretation of susceptibility results for ampicillin, cefotaxime, ceftazidime, gentamicin, and trimethoprim showed almost perfect concordance between CLSI and EUCAST (κ > 0.91). Conclusions: Variations in the interpretation of antimicrobial susceptibility testing results may influence AMR surveillance outcomes and antimicrobial use decision-making in the field. Strengthening and harmonizing AMR surveillance reporting based on both standards is essential to support evidence-based and effective AMR mitigation policies. This approach, within a One Health framework, is to safeguard animal health, public health, and food safety in Indonesia.