Full Validation of Pooled Antibiotic Susceptibility Testing Using CLSI Methods and Performance Criteria in UTI...

Area of Science:

• Clinical microbiology
• Antimicrobial resistance
• Diagnostic assay validation

Background:

• Complicated, persistent, and recurrent urinary tract infections (UTIs) require accurate and rapid antimicrobial susceptibility testing.
• Existing methods may not be sufficiently rapid or comprehensive for complex UTI cases.
• Pooled Antibiotic Susceptibility Testing (P-AST) is a novel assay designed to address these challenges.

Purpose of the Study:

• To validate the performance of the P-AST assay for identifying uropathogenic bacteria.
• To assess P-AST against established Clinical and Laboratory Standards Institute (CLSI) protocols and performance metrics.
• To evaluate P-AST for both monomicrobial and polymicrobial urine specimens.

Main Methods:

• P-AST was validated against standard disk diffusion and broth microdilution reference methods.
• Performance was evaluated across five groups of uropathogenic organisms (Enterobacterales, Enterococci, Staphylococci, Pseudomonas aeruginosa, Acinetobacter species).
• Testing included fresh and frozen clinical urine specimens, as well as contrived specimens, against up to 20 relevant antibiotics.

Main Results:

• P-AST met CLSI performance criteria, including ≥90.0% categorical agreement and low error rates (<3.0% very major and major errors).
• Precision exceeded 95.0% across all analysis groups.
• Minimal errors were observed in both monomicrobial and polymicrobial analyses, with no more than a single very major or major error per organism-antibiotic pair.

Conclusions:

• The P-AST assay, a component of the Guidance® UTI assay, demonstrates acceptable performance for antibiotic susceptibility testing.
• P-AST meets CLSI thresholds when compared to standard and reference methods.
• The assay is suitable for both monomicrobial and polymicrobial specimens, supporting its use in complex UTI cases.