SIST EN ISO 20776-1:2020 PDF

Overview

EN ISO 20776-1:2020 (identical to ISO 20776-1:2019, corrected 2019-12) defines the broth micro-dilution reference method for determining minimum inhibitory concentrations (MICs) of antimicrobial agents against rapidly growing aerobic bacteria. The standard describes a standardized in vitro procedure used in antimicrobial susceptibility testing (AST) to quantify the activity of antimicrobial agents under controlled conditions. It is a reference method for validating other susceptibility methods and devices (e.g., disc diffusion, diagnostic test devices).

Key topics and technical requirements

• Test method: Detailed broth micro-dilution procedures including preparation of micro-dilution trays, stock and working solutions of antimicrobial agents, inoculum preparation (broth culture and colony suspension methods), inoculation, incubation and result reading.
• Medium: Requirements and guidance for standardized Mueller‑Hinton broth (including Annex A) and possible modifications for certain agents.
• Antimicrobial preparations: Solvents, diluents and storage for stock and working solutions (see Annex B and Annex C); corrected values are noted (e.g., ampicillin diluent pH correction in the corrected 2019-12 text).
• Quality control: Procedures to ensure reproducibility and reliability of MIC results across laboratories and over time.
• Special situations: Guidance on test situations that may produce unreliable MICs and recommended modifications (Annex D).
• Scope limits: The document focuses on MIC determination and method performance; clinical interpretation (defining clinical breakpoints S/I/R) is addressed separately and not defined within this standard.

Applications and who uses it

• Clinical microbiology laboratories use the method for precise MIC determination when quantitative results are required for patient management, epidemiology, or when routine tests are equivocal.
• Manufacturers of antimicrobial susceptibility test devices and in vitro diagnostic systems use EN ISO 20776-1:2020 as the reference method to validate and compare their devices against a recognized standard.
• Regulatory bodies and accreditation organizations reference this standard when assessing method conformity, device performance and lab quality systems.
• Public health and surveillance programs use MIC data produced to monitor resistance trends and to distinguish wild-type from non-wild-type bacterial populations.
• Research laboratories conducting comparative testing of new antimicrobial agents or pharmacodynamic studies.

Related standards

• Other parts of the ISO 20776 series cover evaluation and specific device performance and complementary methods; EN ISO 20776-1:2020 is intended as the laboratory reference for broth micro-dilution AST.

Keywords: EN ISO 20776-1:2020, ISO 20776-1:2019, broth micro-dilution, antimicrobial susceptibility testing, MIC, Mueller‑Hinton broth, AST, diagnostic devices, in vitro activity.