The who’s who of microorganisms

Cosmetics that are harmless to health are a must; safety and stability are guaranteed by EU Regulation 1223/20091. Microbiological product stability as well as microbiological purity and safety are important components.

This article is intended to show which microorganisms are frequently detected in cosmetics. The focus is placed on the occurrence, the properties, and a classification with regard to the hazard potential. The basis for this is, on the one hand, data from the European rapid alert system Safety Gate2 and evaluations of numerous product and raw material tests from the BAV Institute3. It is important to mention that the germs presented below are only a selection and the list cannot be exhaustive. For all microbiological product tests, compliance with the limit values of ISO 175164 should be noted. 

In the event of a positive microbiological finding, an individual risk assessment must always be carried out for each product. This requires identification of the microorganisms detected. Depending on the result of this risk assessment, subsequent tests, a blocking of the goods, or even a recall of the goods are possible.

In general, it can be observed that bacteria play a greater role than yeasts and moulds about possible contamination of cosmetics. In the following, common bacteria are examined in more detail:

Pseudomonas aeruginosa (P. aeruginosa)

The genus Pseudomonas comprises several species, of which P. aeruginosa has the greatest relevance in the cosmetics sector. Thus, it is also a regulatory requirement that P. aeruginosa must not be detectable in one  gram of product (ISO 17516,4). Pseudomonads are gram-negative, motile rods. P. aeruginosa is also classified in risk group 2 (can cause diseases in humans)5.

Pseudomonads have the property of being relatively undemanding to external living conditions and can thus survive for a long time in humid but also dry environments. In the cosmetic manufacturing industry, they can occur wherever there is sufficient water (washrooms, pipelines and equipment with residual moisture, a water system, etc.). 

The ability to form biofilms is particularly critical. The detachment of individual parts of the biofilm, which are then irregularly distributed in the product, is a frequently observed phenomenon. This makes detection in finished cosmetic products difficult (uneven distribution).

Pluralibacter gergoviae (P. gergoviae)

This microorganism (former name Enterobacter gergoviae) belongs to the Enterobacteriaceae family and it is a gram-negative rod (bacterium). It is widespread in the environment and is facultatively pathogenic (in contact with open wounds, infection cannot be ruled out). An increase in product recalls due to contamination with P. gergoviae has been observed in recent years (including shampoos, creams, shower gels, etc.). In a statement of the BfR from 20206, the absence of this bacterium in cosmetics is therefore demanded (for further information, see also publications of the DGK,7).

This germ is also known for the so-called “phoenix effect”, i.e., a contamination that was thought to have disappeared reappears after a certain time, usually in very high numbers. P. gergoviae also has the property of adapting to certain preservatives (adaptation) and forming biofilms. Entry into cosmetic products usually occurs via contaminated water or inadequate hygienic conditions.

Burkholderica cepacia (B. cepacia)

This microorganism belongs to the Burkholderiaceae family. It is a gramnegative rod that occurs ubiquitously in the environment (preferably in water). This germ is undemanding about available nutrients and can even survive in disinfectant solutions. As with the two microorganisms mentioned above, the main source of entry is primarily contaminated water or inadequate hygienic conditions.

Just like P. aeruginosa and P. gergoviae, B. cepacia, is able to form biofilms and thus lead to an irregular entry of microorganisms into products. One noteworthy entry from 2018 was associated with a report by the RKI regarding an increased occurrence in clinics (the most likely source of germs was a mouth rinsing solution, which was used in all cases).

Bacillus cereus (B.cereus)

Bacillus cereus and other Bacillus species are gram-positive, rod-shaped bacteria. These microorganisms are also widely distributed in the environment. Bacilli can form resistant forms (so-called spores). These spores are very heat stable and can survive heating steps. Because the number of ba-cilli in a contaminated product usually remains relatively stable over a long period of time and that they are not to be considered pathogenic for cosmetics, detection is rather uncritical. Nevertheless, clarification of the source of entry is important. 

In contrast to the previously listed gram-negative bacteria (P. aeruginosa, P. gergoviae, B. cepacia), the main source of contamination for cosmetics is usually not contaminated water, but other cosmetic raw materials, primarily dry products (powders, granulates, etc.). Inadequate plant hygiene can also be a cause; sufficient cleaning and disinfection (especially regarding the possibility of spore formation) are of particular importance here.

In the following, two microorganisms from the area of yeasts and moulds are explained in more detail. As already mentioned, these play a lesser role than the bacteria mentioned regarding possible contamination associated with a consumer hazard.

Aspergillus brasiliensis (A. brasiliensis)

Aspergillus brasiliensis is a mould that shows a characteristic dark growth on the corresponding culture media (figure 5). Aspergilli also occur ubiquitously in the environment (as well as in the air) and can form so-called mould spores. An entry into cosmetic products also occurs here mostly via contaminated raw materials (see Bacillus) as well as via poor hygiene in the company. 

About a possible consumer hazard due to product contamination, A. brasiliensis also plays a subordinate role. It is used as a representative of the moulds when carrying out the preservation efficacy test according to ISO 119308.

Candida albicans

Candida albicans is classified as a yeast and can cause a so-called candidiasis (disease mainly in the oral cavity), but in most cases the colonisation with C. albicans hardly causes any symptoms. This germ is also detectable in about 75% of all healthy people.

In the cosmetic sector, ISO 17516 requires its absence in one gram of product. This yeast, like other yeasts, plays only a minor role in terms of frequency of detection and potential risk.

Possible sources of entry here are also contaminated raw materials or, to a lesser extent, insufficient hygiene in the company.

References

1 Regulation (EC) No 1223/2009 of the European Parliament and of the Council of 30 November 2009 on cosmetic products, as amended

2 Safety Gate: the EU rapid alert system for dangerous non-food products, www.ec.europa.eu/safety-gate-alerts

3 Microorganisms in cosmetics and raw materials, Fellenberg/Muller, Euro Cosmetics, 5/6-2021

4 ISO 17516: 2014-10, Cosmetic products - Microbiology - Microbiological limits

5 Technical Rules for Biological Agents, Classification of Prokaryotes, TRBA 466, 2015 edition as amended

6 Skin creams, make-up and shampoos should be free of Pluralibacter gergoviae, updated statement no. 038/2020 of 7 September 2020, BfR

7 Recommendation of the DGK specialist group “Microbiology and Industrial Hygiene” on dealing with risks from Pluralibacter gergoviae in cosmetic products, Eigener/Keck-Wilhelm/Nussbaum/Simmering/Staub, statement November 2020, www.dgk-ev.de

8 ISO 11930: 2019-05, Cosmetic products - Microbiology – Evaluation of the antimicrobial protection of a cosmetic product