Pathogen flora in milk - 5 criteria♦ - 2023

Introduction

The proficiency testings and criteria marked with an ♦ are covered by the « accréditation n° 1-2473, comparaisons interlaboratoires, portée disponible sur www.cofrac.fr »/« n° 1-2473 accreditation, interlaboratory comparisons, scope available on www.cofrac.fr », and detailed flexible scope available there

We propose tests for the enumeration of Listeria monocytogenes in milk and cheese which must not be mistaken for tests for detection of Listeria.

The tests for the detection of Salmonella do not concern Salmonella Typhi and Paratyphi.

The enumeration of sulphite-reducing anaerobes, Clostridium perfringens and Bacillus cereus concerns non-spore-forming bacteria. The analysis must be carried out without heat treatment.

We draw your attention to the fact that we don't contaminate our samples with collection strains but with strains isolated from dairy food matrices. Therefore, it is possible that some of them present unexpected phenotypic characteristics on some culture media.

Methods / Analytes

→  detection of Listeria♦ and Salmonella♦

→ enumeration of coagulase positive staphylococci♦, Escherichia coli♦ and Bacillus cereus♦

free choice for methods

Number of samples

→ 5 samples for the detection of:
- Listeria in 25 ml of milk and identification of the species, included Listeria monocytogenes
- Salmonella in 25 ml of milk

→ 5 samples containing between:
- 0 and 10 000 coagulase positive staphylococci/ml
- 0 and 100 000 Escherichia coli/ml

→ 5 samples containing between:
- 0 and 30 000 Bacillus cereus (without thermisation)/ml

→ 1 vial of water to control the temperature of the samples at reception

Packaging

- five 60 ml screw-capped vials for the detection of Listeria and Salmonella
- five 30 ml screw-capped vials with airtight seals, for the enumeration of Staphylococci and Escherichia coli
- five 30 ml screw-capped vials with airtight seals, for the enumeration of Bacillus cereus

Preservation

storage at 3 (±2) °C, with a bacteriostatic mixture preventing any bacterial growth in the milk, but rendered inactive upon dilution.

CAUTION no bacterial growth occurs in the undiluted sample with ready-to-use rehydratable medium (because of the bacteriostatic mixture). It is unnecessary to inoculate this undiluted sample.

Dispatch

in IATA certified secondary packaging, in insulated box with ice packs by express carrier

Storage in the laboratory

at 3 (± 2) °C

Validity of the samples

analyses must be carried out within 3 days after the date of dispatch

Special conditions

International delivery by international carrier

- In Europe: shipping time: 1 to 3 days depending on the consignee’s country and town

- Intercontinental delivery: shipping time is 1 to 4 days depending on the consignee’s country and town, and time before dispatch may take up to 7 days, the time necessary to obtain customs documents

On condition for the dispatch to certain destinations, please contact us concerning this point

Calendar of dispatch :

Subscription at least 10 days before each dispatch

Special conditions :

• For groups from 10 to 24 participating laboratories: 10 % discount,
• For groups from 25 participating laboratories: 15 % discount

Payment conditions :

within 1 month of receiving invoice