Purpose
To standardize Minimum Inhibitory Concentration (MIC) using a validated antimicrobial susceptibility testing method.
Scope
This procedure applies to trained microbiology laboratory personnel working within an approved quality-management and biosafety system.
Principle
The MIC is determined from standardized exposure of an organism to defined antimicrobial concentrations using an approved reference or validated method.
Specimen / Test Material
A suitable, pure and correctly identified isolate prepared according to the validated AST method.
Equipment and Materials
- Validated AST media or broth
- Standardized inoculum preparation materials
- Approved antimicrobial agents or disks
- Incubation system
- Quality-control organisms
- Current approved breakpoint tables
Procedure
- Select a suitable pure isolate.
- Prepare standardized inoculum.
- Set up the validated MIC concentration range or commercial system.
- Incubate according to the approved method.
- Determine the endpoint according to validated reading rules.
- Apply current breakpoint interpretation where clinically applicable.
Quality Control and Quality Assurance
- Use appropriate QC strains.
- Monitor reagent, panel and instrument performance.
- Do not interpret results when required QC is unacceptable.
Reporting
Report results only after confirming acceptable quality-control performance and applying the current laboratory-approved interpretive criteria.
Safety
Use risk-based biosafety practices, appropriate personal protective equipment and approved decontamination and waste-disposal procedures. Treat clinical specimens and cultures according to the laboratory's biological risk assessment.
References
- World Health Organization (WHO): Toolkit for Standard Operating Procedures for Bacteriology, Mycology and Antimicrobial Susceptibility Testing.
- WHO: Laboratory Biosafety Manual, 4th edition.
- WHO guidance on collection, packaging and transport of infectious substances.
- EUCAST methodology and quality-control guidance for antimicrobial susceptibility testing, where applicable.
- Current locally approved laboratory procedures and validated manufacturer instructions.