Fact sheet on Staphylococcus aureus

General information
Staphylococcus aureus (S. aureus) is a bacterium that commonly occurs on the skin and mucous membranes of humans and animals. It belongs to the group of coagulase-positive staphylococci.
In cosmetic products S. aureus is feared because it can cause skin and wound infections, abscesses and urinary tract infections. In cosmetics, according to ISO 17516, the absence of S. aureus in 1 g is required.

Characteristics

• Cocci-shaped bacteria
• Gram-positive
• Oxidase-negative
• Catalase-positive
• Toxin producer

Origin / Occurrence

• Natural component of the skin flora of humans (particularly the scalp and hair) and on the mucous membranes of the nasopharynx (e.g., nasal secretions and saliva).
• Occurrence in high cell counts if the pathogen is responsible for infections in the nasopharynx or wound infections.
• Also occurs in farm and companion animals.
• Due to their wide distribution in humans and animals, these microbes are also regularly found in our environment.

Significance

• S. aureus is a potential infectious agent in cosmetics (especially on damaged skin and for applications in the nose, mouth and ear areas).
• Hygiene indicator → poor personnel hygiene
• Relatively resistant to drying (relevant for dried raw materials).

Important note

• There are also antibiotic-resistant strains (methicillin-resistant Staphylococcus aureus – MRSA), which can, for example, cause severe wound infections.

Growth conditions

• Temperature:
  
  • Optimum: +35 °C to +40 °C
  • Minimum: +6 °C
  • Generally no growth above +50 °C
• pH value: Growth at pH 4.5 to 9.3 (exceptions even down to pH 4.0).
• a_w value: According to ISO standard 29621, cosmetics with an a_w value of 0.75 are considered higher risk, as most bacteria can multiply at this water activity (relatively resistant to drying).
• Salt tolerance: up to max. 20%; multiplication still at 6.5 to 10%
• Oxygen requirement: Growth with and without oxygen (facultative anaerobe).

Inactivation by heating

• At +72 °C for a minimum exposure time of 2 minutes (Note: monitor core temperature).

1. Review cleaning and disinfection procedures:
   1. Hygiene plan including
   2. Details on the execution of cleaning and disinfection, e.g., disinfectant dosing, contact time, use of suitable and clean materials and cleaning cloths
   3. Specifications for cleaning and disinfection for all product-contact systems and auxiliary items
2. Train employees 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 incoming goods for e.g., incoming/transport temperature, shelf life, packaging, deviations or microbiological abnormalities
2. This also applies to goods before use in production. In case of suspicion, do not use raw materials and ingredients
3. Review microbiological specifications. If necessary, request laboratory testing of suspicious products or obtain results from the supplier
4. Verify by follow-up testing

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

1. Train employees regarding potential errors and corrective measures
2. Check the changing and cleanliness of work clothing
3. Verify by on-site inspections and follow-up testing (e.g., contact plate and swab tests)

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

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

1. Review processes, production protocols and documentation
2. Inactivation of most microorganisms at a core temperature of +72 °C for a minimum of 2 minutes
3. Verify by follow-up testing

1. Perform preservative efficacy test (challenge test)
2. Adjust the preservation system if necessary
3. Verify by repeating the preservative efficacy test