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Susceptibility testing. Phenotypic and genotypic tests for bacteria and mycobacteria
1Department of Laboratory Medicine and Pathology, University of Alberta, Provincial Laboratory of Public Health (Microbiology), University of Alberta Hospital, Edmonton, Alberta, Canada.
Infectious Disease Clinics of North America
|January 10, 2002
Summary
Genotypic antimicrobial resistance detection offers speed but has limitations. Phenotypic methods remain crucial for complex resistance mechanisms and confirming susceptibility, requiring careful clinical validation.
Area of Science:
- Clinical Microbiology
- Molecular Diagnostics
- Infectious Diseases
Background:
- Genotypic methods show potential for rapid antimicrobial resistance detection.
- Phenotypic methods are still advantageous for complex resistance mechanisms.
- Current molecular technology may not cover the diversity of genetic resistance mechanisms.
Purpose of the Study:
- To evaluate the role and limitations of genotypic methods in antimicrobial resistance detection.
- To compare genotypic and phenotypic approaches in clinical settings.
- To highlight considerations for implementing genotypic assays in clinical laboratories.
Main Methods:
- Review of genotypic and phenotypic antimicrobial resistance detection methods.
- Discussion of molecular assay limitations including false positives and standardization issues.
- Emphasis on the need for clinical validation of genotypic assays.
Main Results:
- Genotypic assays detect resistance but not susceptibility.
- Molecular methods can be labor-intensive, expensive, and lack standardization.
- False-positive results are a risk due to contamination and carryover.
Conclusions:
- Genotypic methods require careful interpretation due to potential confounding factors like normal flora.
- Cost, turnaround time, and assay performance are key considerations for implementation.
- Bedside patient assessment remains essential alongside any susceptibility testing results.