Multisite evaluation of blAST, a direct-from-urine phenotypic antimicrobial susceptibility test, compared with...

Area of Science:

• Clinical microbiology
• Antimicrobial resistance
• Diagnostic assay development

Background:

• Traditional antimicrobial susceptibility testing (AST) is slow and requires bacterial isolation.
• A novel, rapid phenotypic AST method, Bio-Labeling Antibiotic Susceptibility Test (blAST), utilizes non-canonical amino acid incorporation and click chemistry.
• blAST offers population-level, direct-sample testing in approximately 6 hours.

Purpose of the Study:

• To evaluate the performance of blAST against urinary tract infection (UTI) pathogen isolates and direct clinical urine samples.
• To compare blAST results with reference broth microdilution (rBMD) across multiple study sites.
• To assess the clinical utility of blAST for rapid UTI diagnostics.

Main Methods:

• Multi-site evaluation of blAST on reference and challenge bacterial strains.
• Direct testing of urine samples from suspected UTI patients (N=740) and healthy donors (N=12) for 9 antibacterials.
• Comparison of blAST results with isolate-based rBMD for susceptibility/resistance interpretation.

Main Results:

• blAST demonstrated >92% between-site reproducibility on reference strains and >80% agreement with rBMD on challenge strains (excluding nitrofurantoin).
• Concordance between blAST and rBMD on clinical UTI samples was 62%, with blAST often detecting resistance missed by isolate-based rBMD.
• Retesting of discordant isolates by blAST showed ~99% agreement with rBMD, indicating high isolate-level accuracy.

Conclusions:

• blAST is a reproducible, rapid phenotypic AST method with strong agreement to rBMD on bacterial isolates.
• Direct sample testing with blAST identified resistance in whole urine samples not detected by isolate-based methods.
• Population-level direct-sample AST results may differ from isolate-based protocols, necessitating further investigation for clinical application.