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ISO 22718

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ISO 22718

ISO 22718 is a standardised microbiological analysis method published by the International Organisation for Standardisation (ISO) for the detection of Staphylococcus aureus in cosmetic products. The full title of the standard is ‘Cosmetics – Microbiology – Detection of Staphylococcus aureus’.

Current version: The base text of ISO 22718:2015, together with Amendment 1 (ISO 22718:2015/Amd 1:2022), is in force. Consolidated editions (e.g. DIN EN ISO 22718:2023-01, ÖNORM EN ISO 22718:2023 03 01) were published by the European standardisation organisations in 2022–2023. It is therefore crucial that the current consolidated version is used as the basis for the work[reference:0][reference:1].

Staphylococcus aureus is a Gram-positive, coccus-shaped, catalase-positive and coagulase-positive bacterium. Its presence in cosmetic products poses a risk to consumer health, particularly in products that come into contact with the skin and mucous membranes. The ISO 22718 standard is applied in conjunction with ISO 17516 (Cosmetics – Microbiology – Microbiological limit values); ISO 17516 stipulates that S. aureus must not be present in cosmetic products (absence in a specified sample size).

ISO 22718, together with other standards relating to the microbiological evaluation of cosmetics, forms a series of standards:

  • ISO 21149 – Enumeration and detection of aerobic mesophilic bacteria
  • ISO 21150 – Detection of Candida albicans
  • ISO 22717 – Detection of Pseudomonas aeruginosa
  • ISO 22718 – Detection of Staphylococcus aureus
  • ISO 21527 – Enumeration of yeasts and moulds
  • ISO 11930 – Testing of preservative efficacy (challenge test)

The basic principle of the standard consists of the enrichment and verification phases:

1. Enrichment

  • The sample is homogenised in a suitable diluent and inoculated into a non-selective liquid culture medium (enrichment broth).
  • Incubation usually takes place under aerobic conditions at 37 °C ± 2 °C for 24–48 hours.
  • Non-selective enrichment allows potential S. aureus cells (and other microorganisms) to multiply; this is followed by the selective isolation phase[reference:2].

2. Isolation on selective agar

  • Aus der Anreicherungsbrühe wird auf ein selektives Festnährmedium (z. B. Baird-Parker-Agar, Mannitol-Salz-Agar, chromogenes Agar) überführt.
  • Incubation takes 24–48 hours at 37 °C ± 2 °C.
  • S. aureus exhibits a typical colony morphology (e.g. on Baird-Parker agar, black, glossy and surrounded by a clear halo; on chromogenic agar, characteristic colouration)[Reference:3].

3. Confirmation

  • Suspicious colonies are confirmed by means of the coagulase test, the catalase test and, where appropriate, biochemical tests (e.g. DNase, mannitol fermentation).
  • Alternatively, molecular methods (PCR, qPCR, MALDI-TOF-MS) can be used.
  • Coagulase-positive isolates with typical morphology are classified as S. aureus-positive.

The method is validated in accordance with ISO 21148 (Cosmetics – Microbiology – General guidelines); the influence of the product matrix (preservatives, pH, surfactants) on enrichment, isolation and identification must be assessed.

The key parameters reported in the study are as follows:

    • Test result (present/absent) and corresponding sample size (usually 1 g or 1 mL)
    • Diluent, enrichment broth and selective agar used
    • Incubation temperature and duration (for each phase)
    • Morphological characteristics

the suspect colonies

  • Confirmatory tests (coagulase, catalase, biochemical, molecular) and their results
  • Comparison with the limit values specified in ISO 17516
  • Conditions for sample preparation (homogenisation, neutralisation)
  • Information on method validation (in accordance with ISO 21148)
  • Positive and negative controls
  • Data on measurement uncertainty and repeatability

Why is it carried out?

Testing in accordance with ISO 22718 is carried out for the following scientific, technical and regulatory purposes:

  • Ensuring consumer safety: Detection and prevention of S. aureus contamination in cosmetic products
  • Demonstration of compliance with the limit values specified in ISO 17516: Assessment of the requirement that S. aureus must not be detectable in a specified sample volume
  • Quality control: Monitoring microbiological consistency between production batches
  • Raw Material Control: Assessment of the microbiological quality of cosmetic raw materials
  • Demonstration of the effectiveness of the preservative system: Provision of baseline data for the evaluation of the effectiveness of preservatives (ISO 11930)
  • Stability and shelf-life assessment: Monitoring the risk of contamination by S. aureus during storage
  • Support with the preparation of authorisation documentation: provision of data for the Cosmetic Product Safety Report (CPSR) in accordance with the EU Cosmetics Regulation (EC 1223/2009) and the relevant national regulations
  • GMP compliance: Demonstration of production hygiene in accordance with ISO 22716 (Cosmetics GMP)
  • Evidence-based approach: a contribution to the holistic assessment of the product in conjunction with other microbiological tests, tests on the efficacy of preservatives and stability data

ISO 22718 alone does not guarantee complete product safety.
The total count of aerobic mesophilic bacteria (ISO 21149), the detection of other pathogens (ISO 21150, ISO 22717) and the assessment of preservative efficacy (ISO 11930) must be evaluated in accordance with separate standards. The results should be interpreted in the context of the product formulation, production conditions, and packaging and storage conditions.

As part of our Nano-Test service, we carry out S. aureus detection tests in accordance with ISO 22718, utilising our accredited laboratory facilities and quality management system, and applying scientific rigour. Our scope of services includes the following:

Method selection and validation

  • Selection of the appropriate diluent, enrichment broth and selective agar, depending on the product type and its physico-chemical properties
  • Determination of the sample preparation strategy (homogenisation, neutralisation)
  • Method validation (in accordance with ISO 21148): accuracy, repeatability and reproducibility
  • Determination of the verification strategy (biochemical tests, molecular methods)
  • Evaluation and reporting of measurement uncertainty

For information on the selection of methods and culture media, sample acceptance criteria, and comparison with the limit values specified in ISO 17516, the testing schedule and the reporting procedures for your S. aureus detection tests in accordance with ISO 22718, please feel free to contact Nano-Test.

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