Purpose
To standardize Broth Dilution Method 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
A standardized organism inoculum is exposed to a series of antimicrobial concentrations in broth, allowing assessment of growth inhibition.
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
- Prepare the validated concentration series or approved testing panel.
- Prepare a standardized inoculum.
- Inoculate according to the validated method.
- Incubate under method-specific conditions.
- Examine growth endpoints using the approved reading criteria.
- Determine the relevant susceptibility endpoint where applicable.
- Interpret using the current approved standard.
Quality Control and Quality Assurance
- Verify concentration preparation or panel integrity.
- Use required QC organisms.
- Confirm acceptable media and incubation performance.
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.