Pooled Antibiotic Susceptibility Testing Performs Within CLSI Standards for Validation When Measured Against Broth...

Area of Science:

• Microbiology
• Clinical Diagnostics
• Antimicrobial Resistance

Background:

• New antimicrobial susceptibility testing methods require validation against standard protocols for accuracy and error rates.
• Complicated and recurrent urinary tract infections (UTIs) necessitate reliable diagnostic tools.

Purpose of the Study:

• To validate a novel pooled antibiotic susceptibility testing (P-AST) assay for UTIs.
• To compare P-AST performance against broth microdilution (BMD) and disk diffusion (DD) using Clinical and Laboratory Standards Institute (CLSI) guidelines.

Main Methods:

• Consecutive clinical urine specimens were analyzed using standard urine culture, multiplex polymerase chain reaction (M-PCR), and P-AST.
• Antibiotic susceptibility testing (AST) was performed in parallel using P-AST, BMD, and DD.
• Analysis included assessment of heteroresistance for discrepant results.

Main Results:

• P-AST demonstrated essential agreement (EA%) ≥90% and met CLSI thresholds for very major errors (VMEs) <1.5% and major errors (MEs) <3.0% without heteroresistance correction.
• Categorical agreement (CA%) exceeded 88%, with most errors being minor.
• VME and ME rates decreased to <1.0% for P-AST when heteroresistance was accounted for.

Conclusions:

• The P-AST assay is validated within acceptable parameters according to CLSI criteria.
• P-AST shows comparable performance to BMD and DD for UTI diagnostics.
• The assay's accuracy is further improved by accounting for heteroresistance.