Cosmetics testing - Microbiology of cosmetics. Strict anaerobic bacteria detection and counting
(method recommended by the FDA, USA)
The test allows to know the total number of strict anaerobic bacteria per unit volume (mL) or weight (grams) of the cosmetic and the results are expressed in CFU (colony forming units). To perform the test, the cosmetic is diluted in a validated neutralizing solution. At the same time, the product is subjected to an enrichment culture to facilitate growth of some bacteria that may be present in low number. Dilutions of the product in the diluent-neutralizing solution and in the enrichment culture are seeded on a solid medium suitable for anaerobic bacteria and incubated for 72 hours at 35ºC in anaerobiosis. Validation of neutralization should also be conducted to detect the presence of inhibitors of microorganisms in the cosmetic that may mask the presence of bacteria by culturing, treating with a neutralizer and inoculated with bacterial strains whose growth corroborates that have been correctly neutralized the inhibitors.