ISO 11290-2:2017

Overview

ISO 11290-2:2017 - Microbiology of the food chain - Part 2: Enumeration method - specifies a horizontal laboratory procedure for the enumeration of Listeria monocytogenes and Listeria spp. in food, feed and food‑production environment samples. The standard defines the five key stages of the method (initial suspension, surface plating, incubation, confirmation and enumeration) and sets out requirements for media, equipment, sampling and result expression.

Key topics and technical requirements

• Scope: Enumeration of L. monocytogenes and Listeria spp. (including L. monocytogenes) in products intended for human/animal consumption and environmental samples from food production/handling areas.
• Principle: Prepare initial suspension and perform surface plating (Agar Listeria - Ottaviani and Agosti), incubate and confirm presumptive colonies, then calculate colony‑forming units (cfu) per g, mL, cm2 or per sampling device.
• Sampling & preparation: Follow ISO 6887 (sample preparation and decimal dilutions) and ISO 7218 for general laboratory practice. Primary suspension media referenced (e.g., buffered peptone water, half‑Fraser broth) are described in the standard.
• Incubation: Plates incubated at 37 °C with examination after 24 h and again after a further 24 h (the document also references incubator ranges and optional conditions).
• Confirmation: Presumptive colonies require morphological and/or biochemical confirmation; certain tests (microscopy, catalase, CAMP) are noted as optional in this edition.
• Results & performance: Enumeration is based on the number of confirmed colonies; the standard includes performance characteristics, validation data and statistical repeatability/reproducibility information.
• Safety & quality: Recommends testing in laboratories with biosafety level 2 conditions, and adherence to ISO 11133 for culture media quality and ISO 7218 for laboratory requirements. Quality assurance and reporting requirements are specified.

Applications and who uses it

ISO 11290-2:2017 is used by:

• Food and feed manufacturers (QA/QC teams) for routine product testing.
• Environmental monitoring programs in food-processing facilities (surface swabs).
• Contract microbiology laboratories conducting regulatory or customer testing.
• Public health and regulatory agencies for food safety surveillance and compliance.
  Practical uses include enumeration in ready‑to‑eat (RTE) foods, dairy, meat, seafood, processed foods, animal feed and environmental hygiene verification.

Related standards

• ISO 11290-1 (detection method for Listeria)
• ISO 6887 (sample preparation and dilutions)
• ISO 7218 (general microbiology laboratory requirements)
• ISO 11133 (culture media preparation and performance)

ISO 11290-2:2017 is a core reference for laboratories and food safety professionals seeking a harmonized, validated approach to Listeria enumeration in the food chain.