🦠 Listeria monocytogenes and Listeria spp. — DETECTION to PN-EN ISO 11290-1

Microbiology PN-EN ISO 11290-1

Overview

SCALE AND PLACE IN THE SERIES. Measurement of 22 Sep 2026: 138 entries at 79 laboratories; matching by the BEGINNING of the recorded string gives 135 entries at 77 laboratories. This is PART 1 — the DETECTION method (the answer "present / absent" in a defined mass of sample). Part 2 is a separate document describing ENUMERATION (a result in cfu per gram or millilitre) — it has its own article in this database. The two tests answer two different questions and do not replace one another: in food legislation the criterion is sometimes framed as absence in 25 g, sometimes as a numerical limit.

STATUS (state of the PKN cards on 22 Sep 2026). PN-EN ISO 11290-1:2017-07 — CURRENT, card with no withdrawal note. ICS 07.100.30, technical body KT 3 (Microbiology of the Food Chain), "Implements: EN ISO 11290-1:2017 [IDT], ISO 11290-1:2017 [IDT]". It replaces PN-EN ISO 11290-1:1999 (Polish version) and its amendment PN-EN ISO 11290-1:1999/A1:2005.

TWO LANGUAGE VERSIONS — AND THREE AND A HALF YEARS BETWEEN THEM. The PKN catalogue holds two cards for the same edition: • the ENGLISH version — published 18 Jul 2017, 50 pages; • the POLISH version — published 7 Jan 2021, 42 pages. The previous edition (1999) was withdrawn on 18 Jul 2017, that is, on the day the English version appeared. For three and a half years the edition in force existed in the Polish collection in English ONLY — and only then did the Polish version follow. This is a mechanism worth remembering at any standard: the absence of a Polish version today does not mean there will never be one, and its appearance changes neither the number nor the date of the edition. The date of publication on the card of the Polish version (7 Jan 2021) is not the date on which the standard entered the collection.

WHAT THE 2017 EDITION CHANGED — THREE THINGS VISIBLE IN THE SCOPE ITSELF. The 1999 edition described a "horizontal method for the detection of Listeria monocytogenes", applied to food products and feed. The edition in force gives a method: • for detecting L. monocytogenes AND for detecting Listeria spp. (including L. monocytogenes) — testing of the whole GENUS is therefore added, not only of a single species; • applied to products intended for human consumption and for animal feeding AND to ENVIRONMENTAL SAMPLES taken in the area of food production and food handling — swabs from the production line are added, which the 1999 edition did not cover; • with the reservation that SOME additionally described species of Listeria may not be detected or confirmed by this method. That last reservation is stated expressly in the standard and matters for a result of "Listeria spp. absent": the statement does not say that there is no listeria at all in the sample, only that the method did not detect those it detects.

WHY ENVIRONMENTAL SWABS MATTER IN THIS STANDARD. Listeria monocytogenes persists in a plant — in drains, on floors, in machinery — and travels from there into the product. Bringing environmental samples within the scope of the standard means that testing of the production line can be performed by a standardised and accredited method, and not only by an in-house procedure. This shows plainly in the accreditation scopes: separate entries carry the test object "Environmental samples from food-production and food-handling areas: - swab".

WHAT THE ACCREDITATION SCOPES SHOW. Methodology: "Presence of Listeria monocytogenes" (79 entries), with the technique "Culture method with biochemical confirmation" added (12), "Presence of Listeria spp." (9 + 3 with the technique), "Presence of Listeria monocytogenes and other Listeria spp." (5), both presences named separately in one row (4). This shows that the 2017 extension of scope has actually entered the scopes: laboratories accredit both the species and the genus. The test object is sometimes named as a single matrix ("Meat and meat products"), sometimes as "Food" with a footnote reference, and sometimes as a long list of a dozen or more groups — from meat and milk to herbs, spices and beverages. The method is HORIZONTAL, that is, designed for use with many matrices, and it is accredited accordingly.

FORMS OF THE RECORDED STRING — EIGHT VARIANTS, ONE OF THEM MISLEADING. The standard appears as: "PN-EN ISO 11290-1:2017-07" (112 entries), "PN-EN ISO 11290-1" without the year (18), "PN-EN ISO 11290-1 4)" and "PN-EN ISO 11290-1 2)" — with a FOOTNOTE number stuck to the designation (2 each), "PN-EN ISO-11290-1:2017-07" with a superfluous hyphen (1), "PN-EN ISO 11290-1: 2017-07" with a space after the colon (1), "PN–EN ISO 11290-1:2017-07" with an en dash (1) and "PN- EN ISO 11290-1:2017-07" with a space after the hyphen (1). The form with the attached footnote ("11290-1 4)") is a special case: the digit does not belong to the designation of the standard but to a footnote in the scope table, and in machine reading of the scopes it becomes part of the number. With the 18 entries lacking a year, the edition has to be established separately — the 1999 edition has been withdrawn since 18 Jul 2017.

WHAT THIS ARTICLE DOES NOT SETTLE. We do not have the text of the standard — the description comes from the scope descriptions on the PKN catalogue cards (the 1999 and 2017 editions in both language versions) and from measurement on the accreditation scopes. We therefore do not know: the composition of the enrichment and selective media (including the semi-selective first enrichment stage), the times and temperatures of incubation, the mass of the test portion, the manner of confirming isolates or the reading criteria. Nor have we established whether an amendment (Amd) has been issued to the 2017 edition — in the PKN catalogue we found only amendment A1:2005 to the 1999 edition.

Method principle

The method is culture-based and multi-stage: a weighed portion of sample is suspended in a semi-selective enrichment medium and incubated, then transferred to a selective enrichment medium; from that, streaking is carried out onto two solid selective media. Colonies of typical appearance are confirmed by tests giving a decision at species level (L. monocytogenes) or at genus level (Listeria spp.). The result is expressed as presence or absence in a defined mass or volume of sample — not as a number of micro-organisms.

Applications

• Testing of ready-to-eat food against the safety criterion (absence in 25 g)
• Testing of feed and of raw materials for animal feeding
• Monitoring of the production environment — swabs from lines, floors and drains in food plants
• Testing under HACCP systems and the producer's sampling plans
• Epidemiological investigations — establishing the source of contamination in a plant

Key parameters

Standard

Standard number

PN-EN ISO 11290-1:2017-07 (wersje angielska i polska; wprowadza EN ISO 11290-1:2017 [IDT] i ISO 11290-1:2017 [IDT])

Title (PL)

Mikrobiologia łańcucha żywnościowego — Horyzontalna metoda wykrywania i oznaczania liczby Listeria monocytogenes oraz Listeria spp. — Część 1: Metoda wykrywania

Title (EN)

Microbiology of the food chain — Horizontal method for the detection and enumeration of Listeria monocytogenes and of Listeria spp. — Part 1: Detection method

Step-by-step procedure

1. Establishing what the order concerns: detection or enumeration

   This standard answers the question "is it there" in a defined mass of sample. If the criterion requires a number in cfu/g, part 2 of the series is needed, not this standard.

2. Establishing whether the species or the genus is tested for

   The 2017 edition covers detection of L. monocytogenes AND of Listeria spp. These are two different results; in the accreditation scopes they are sometimes named as separate methodologies and may not both be accredited.

3. Taking the sample — product or production environment

   The standard covers products for human consumption, products for animal feeding and environmental samples from the area of food production and handling. A swab from the production line is a test under the same standard as the product.

4. First enrichment in the semi-selective medium

   The stage of resuscitating injured cells — important for processed, frozen and heat-treated food, where bacteria may be weakened but still able to multiply.

5. Second enrichment in the selective medium

   Further limitation of the accompanying microflora before streaking onto the solid media.

6. Streaking onto two solid selective media and reading

   The standard provides for two solid media; typical colonies are selected for confirmation. The reading conditions are given by the standard.

7. Confirmation of isolates

   Confirmation decides whether the isolate is L. monocytogenes or another Listeria spp. In the accreditation scopes this stage is sometimes called "biochemical confirmation".

8. Reporting the result and the reservation

   The result is reported as presence or absence in a defined mass or volume. For a result concerning the genus it is worth remembering the reservation from the standard's scope: some additionally described species of Listeria may not be detected or confirmed by this method.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• A result of "absent" concerns a defined mass of sample and what the method detects — it is not a pronouncement that there are no bacteria in the whole batch of product
• Detection (part 1) and enumeration (part 2) are two different tests; the criterion in the legislation indicates which is needed
• An accreditation scope may cover detection of L. monocytogenes without detection of Listeria spp., or the reverse — the methodology has to be checked, not the number of the standard alone
• A citation without a year does not identify the edition; the 1999 edition has been withdrawn since 18 Jul 2017 and covered neither the genus Listeria nor environmental samples
• The Polish version of the edition in force appeared only on 7 Jan 2021 — laboratories implementing the standard earlier worked from the English text
• In the record "PN-EN ISO 11290-1 4)" the digit is a footnote number from the scope table, not part of the designation of the standard

Frequently asked questions