PCPC (formely referred to as Costmetic, Toiletry and Fragrance Association or CTFA):
The Personal Care Products Council provides guidance for preservative efficacy testing in Sections 20, 21, 22 & 23 of their Microbiological Guidelines. Products are categorized as such:
The PCPC guidance is the most stringent preservative efficacy currently available and the testing can be conducted in either mixed or pure suspensions. Inocula consisting of only pure microbial cultures will yield specific data on each test microorganism. When using mixed inocula, closely related types of microorganisms, such as Gram-positive bacteria, Gram-negative bacteria and yeasts and molds should be pooled separately. The PCPC recommends challenging products against between five and seven microorganisms and lists possible optional microorganisms that can be added to the assay. Although sampling is indicated at several time points during 28 days, it also allows for the option of a re-challenge of the product at 56 days.