The next step in determining the safety of cosmetic and personal care products is to determine if any microorganisms that may be present are "objectionable" microorganisms that may be harmful to the consumer. If any microorganisms are found to be present in the product after testing using the CTFA M-1 method or the USP 61 test method or an aerobic plate count, the sample should be further examined for the presence of E. coli, S. aureus, and P. aeruginosa and other objectionable microorganisms as requested.
A brief summary of the CTFA M-2 method is described below:
- Cells from isolated colonies on agar plates that are visible within 24 hours of incubation are gram stained and examined under a microscope to observe cellular morphology indicative of E. coli, S. aureus and P. aeruginosa.
- Colonies that appear after 24 hours are streaked to new agar plates of the same media and incubated for 18-24 hours and then gram stained.
- Cells from the same isolated colonies are streaked to selective or differential media and incubated appropriately to identify characteristics indicative of E. coli, S. aureus and P. aeruginosa and others as deemed necessary.
- Other biochemical tests may be conducted as required for identification of objectionable microorganisms.
- Examples of media used in testing are: Pseudomonas Isolation Agar (PIA), E.M.B. Agar, MacConkey Agar, and Mannitol Salts Agar.
1. Cosmetic, Toiletry, and Fragrance Association 2007. “CTFA Microbiology Guidelines"