Fact sheet on aerobic mesophilic microorganisms

General
The count of aerobic mesophilic microorganisms is often referred to as the "total viable count". It provides information about the number of microorganisms (bacteria, yeasts and moulds) that multiply optimally under aerobic conditions in a temperature range between +30 °C and +40 °C. For cosmetics in general, the limit according to ISO 17516 is 1000 CFU/g. For cosmetics for children under 3 years of age and for applications in sensitive areas such as the eyes, mouth, or the intimate area, the limit for moulds is 100 CFU/g.

→ More specific information on important microorganisms in cosmetics: see other profiles

Origin / Occurrence

• Varies depending on the microorganism: e.g., raw materials, humans, animals, plants, soil, water, air, as well as packaging, work surfaces and equipment

Significance

• Cosmetic products are generally not sterile and may therefore contain microorganisms.
• Aerobic mesophilic microorganisms are, depending on the product type and composition, normal and technologically unavoidable up to a certain number.
• ISO 17516 provides recommendations for limits of aerobic mesophilic microorganisms.
• For cosmetic products that contain plant-derived raw materials, the risk of elevated aerobic mesophilic counts is potentially higher due to the ingredients used.
• If cosmetic products deliberately contain live microorganisms intended to exert a beneficial effect, the total viable count will generally be unavoidably above the assessment values of ISO 17516. This must be taken into account when evaluating test results.
• An increased number of aerobic mesophilic organisms in cosmetics can, for example, be traced back to the following causes:
  • Contaminated raw materials or contaminated water
  • Preservation gaps
  • Insufficient operational hygiene
  • Other potential causes (see section "Causes and measures")

Growth conditions

• Temperature:
  • Optimum: between +30 °C and +40 °C (mesophilic)
  • Minimum: usually +5 to +10 °C (depending on the species, exceptions even down to 0 °C)
  • In general, no growth above +50 °C (exceptions are thermophilic bacteria)
• pH value: growth generally between 5.0 and 9.0 (depending on the species, also possible at significantly lower pH values).
• a_w-value: According to ISO standard 29621, cosmetics with an a_w value of less than 0.75 are considered low-risk, as microorganisms generally can no longer multiply at this water activity.
• Oxygen requirement: many bacteria can grow with and without oxygen (facultative anaerobes). There are also microorganisms that can only multiply under aerobic or anaerobic conditions.

Inactivation by heating

• Most microorganisms are killed at +72 °C for at least 2 minutes (Note: monitor core temperature).
• Thermostable bacteria as well as spores of bacteria and moulds are more heat-resistant (especially bacterial spore formers such as Bacillus pumilus, Bacillus cereus, Bacillus subtilis, Paenibacillus sp.).

1. Check the execution of cleaning and disinfection:
   1. Hygiene plan with information on how to perform cleaning and disinfection, e.g. dosing, contact time, use of appropriate and clean materials and cleaning cloths
2. Train staff regarding potential errors and corrective measures
3. Repeat cleaning and disinfection
4. Verify effectiveness by on-site inspections and follow-up testing (e.g., contact plate and swab tests)

1. Check water systems and piping for correct function and condition. Avoid stagnation of water in e.g. pipes, systems, hoses...
2. Regularly check water systems and piping microbiologically and technically (observe maintenance intervals)
3. In case of contamination of water systems, react immediately and initiate measures. Involve specialized companies if necessary
4. Verify effectiveness by regular follow-up testing

1. Inspect incoming goods for e.g. shelf life, packaging, deviations or microbiological anomalies
2. This also applies to the material before use in production. Do not use raw materials if suspected of being contaminated
3. Check microbiological specifications. If necessary, request laboratory testing of suspicious products or request results from the supplier
4. Verify effectiveness by follow-up testing

1. Ensure compliance with the formulation
2. If necessary, perform a preservative efficacy test (challenge test)
3. If necessary, adjust the preservation system
4. Verify effectiveness by repeating the preservative efficacy test

1. Check and document production processes
2. Train personnel
3. Verify effectiveness by regular microbiological product testing

1. Review work organization in the facility
   1. Separate work areas, equipment and utensils
   2. Separate "clean" and "dirty" areas and activities
2. Train staff regarding potential errors and corrective measures
3. Verify effectiveness by on-site inspections and follow-up testing

1. Test airborne microbial counts and ventilation systems by technical inspection as well as environmental sampling
2. Avoid high humidity and condensate formation
3. Appropriate cleaning and disinfection (see section "Cleaning and disinfection")
4. Train staff regarding potential errors and corrective measures
5. Verify effectiveness by on-site inspections and follow-up testing

1. Train staff regarding hand and personal hygiene, potential errors and behavior when certain illnesses occur
2. Monitor hand hygiene, glove changes and cleanliness of work clothing
3. Verify effectiveness by on-site inspections and follow-up testing (e.g., contact plate and swab tests)