ISO 20776-1:2019 PDF

Susceptibility testing of infectious agents and evaluation of performance of antimicrobial susceptibility test devices — Part 1: Broth micro-dilution reference method for testing the in vitro activity of antimicrobial agents against rapidly growing aerobic bacteria involved in infectious diseases

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Title (English):

ISO 20776-1:2019

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 19
Publication date:: June 5, 2019
Edition:: ISO IS 20776 edition 2 version 1
ICS:: 11.100.20

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Description (English):

This document describes one reference method, broth micro-dilution, for determination of MICs. The MIC can be a guide for the clinician, and reflects the activity of the drug under the described test conditions, by taking into account other factors, such as drug pharmacology, pharmacokinetics, or bacterial resistance mechanisms. This allows categorisation of bacteria as "susceptible" (S), "intermediate" (I), or "resistant" (R). In addition, MIC distributions can be used to define wild type or non-wild type bacterial populations. Although clinical interpretation of the MIC value is beyond the scope of this document, modifications of the basic method are required for certain antimicrobial agent - bacteria combinations to facilitate clinical interpretation. These modifications are included in a separate annex of this document. It is necessary to compare other susceptibility testing methods (e.g. disc diffusion or diagnostic test devices) with this reference method for validation, in order to ensure comparable and reliable results.

Technical details

Technical committee: ISO/TC 212 - Clinical laboratory testing and in vitro diagnostic test systems
SKU: ISO 20776-1:2019

Abstract

Overview

ISO 20776-1:2019 specifies the broth micro-dilution reference method for determining minimum inhibitory concentrations (MICs) of antimicrobial agents against rapidly growing aerobic bacteria involved in infectious diseases. As a reference method for antimicrobial susceptibility testing (AST), it standardizes procedures-media, antimicrobial preparation, inoculum, incubation and result reading-so MICs are reproducible and comparable across laboratories. The method uses micro-dilution trays (final well volume ≤200 µl) and is intended for pure cultures that grow well in standardized Mueller‑Hinton broth.

Key technical topics and requirements

Test format: Broth micro-dilution in polystyrene micro-trays; typical well volumes indicated (e.g., 50 µl working solution + 50 µl inoculum or 100 µl working solution with small inoculum volume).
Medium: Standardized Mueller‑Hinton broth (requirements and special situations addressed in Annex A and D).
Antimicrobial agents: Use of certified powders from manufacturers (potency, lot number, expiry); preparation of stock and working solutions, appropriate solvents/diluents (Annex B and C).
Inoculum preparation: Defined methods (broth culture or direct colony suspension) to achieve standardized colony-forming units per ml (CFU/ml).
Incubation and reading: Defined incubation conditions and procedures for reading visible growth to determine the MIC; guidance on special test situations where MIC may be unreliable.
Quality control: Use of reference strains and QC practices to ensure intra- and inter-laboratory reproducibility (details provided in the main text and annexes).
Scope limits: The document is a laboratory reference method; clinical interpretation (breakpoint setting) is beyond its scope though MICs enable categorization (S, I, R) when interpreted with breakpoints from bodies such as EUCAST or CLSI.

Practical applications and typical users

Clinical microbiology laboratories performing quantitative AST for patient management when MICs are required.
Reference and public-health laboratories conducting surveillance of antimicrobial resistance and defining wild-type MIC distributions.
Manufacturers and evaluators of diagnostic AST devices (disc diffusion, automated systems) who must validate new or alternative methods against this reference broth micro-dilution method.
Research groups comparing new antimicrobial agents or studying resistance mechanisms.

Related standards and notes

Comparable methods and interpretive criteria are published by CLSI and EUCAST; ISO 20776-1 aligns methodologically with these organizations.
Part of ISO/TC 212 (Clinical laboratory testing and in vitro diagnostic test systems) and complements other parts of the ISO 20776 series.
Keywords: ISO 20776-1:2019, broth micro-dilution, MIC, antimicrobial susceptibility testing, Mueller‑Hinton broth, AST validation, clinical microbiology, quality control.

Related standards

Mentioned in the description and other ISO standards

Abstract

Overview

Key technical topics and requirements

Test format: Broth micro-dilution in polystyrene micro-trays; typical well volumes indicated (e.g., 50 µl working solution + 50 µl inoculum or 100 µl working solution with small inoculum volume).
Medium: Standardized Mueller‑Hinton broth (requirements and special situations addressed in Annex A and D).
Antimicrobial agents: Use of certified powders from manufacturers (potency, lot number, expiry); preparation of stock and working solutions, appropriate solvents/diluents (Annex B and C).
Inoculum preparation: Defined methods (broth culture or direct colony suspension) to achieve standardized colony-forming units per ml (CFU/ml).
Incubation and reading: Defined incubation conditions and procedures for reading visible growth to determine the MIC; guidance on special test situations where MIC may be unreliable.
Quality control: Use of reference strains and QC practices to ensure intra- and inter-laboratory reproducibility (details provided in the main text and annexes).
Scope limits: The document is a laboratory reference method; clinical interpretation (breakpoint setting) is beyond its scope though MICs enable categorization (S, I, R) when interpreted with breakpoints from bodies such as EUCAST or CLSI.

Practical applications and typical users

Clinical microbiology laboratories performing quantitative AST for patient management when MICs are required.
Reference and public-health laboratories conducting surveillance of antimicrobial resistance and defining wild-type MIC distributions.
Manufacturers and evaluators of diagnostic AST devices (disc diffusion, automated systems) who must validate new or alternative methods against this reference broth micro-dilution method.
Research groups comparing new antimicrobial agents or studying resistance mechanisms.

Related standards and notes

Comparable methods and interpretive criteria are published by CLSI and EUCAST; ISO 20776-1 aligns methodologically with these organizations.
Part of ISO/TC 212 (Clinical laboratory testing and in vitro diagnostic test systems) and complements other parts of the ISO 20776 series.
Keywords: ISO 20776-1:2019, broth micro-dilution, MIC, antimicrobial susceptibility testing, Mueller‑Hinton broth, AST validation, clinical microbiology, quality control.

ISO 20776-1:2019 PDF

Technical details

Abstract

Overview

Key technical topics and requirements

Practical applications and typical users

Related standards and notes

Related standards

Abstract

Overview

Key technical topics and requirements

Practical applications and typical users

Related standards and notes

Related standards

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