ABSTRACT

This chapter reviews the technologies of two methodologies central to cosmetic microbiology: preservative efficacy determination and microbial content testing. Neutralization of the preservative must occur in the broth to avoid inflated estimates of efficacy. In these procedures, some residual preservative will carry over into the recovery medium and a neutralizer should be used to inactivate the residual and permit the organisms to grow. Media used for the recovery of microbial survivors will have direct effects on estimates of antimicrobial activity. A neutralizer should inactivate a preservative or biocide and allow for unrestrained microbial growth. The goal of antimicrobial efficacy tests is to provide reproducible results to assist in determination of product quality. Unrealistically high inocula are used to assist the technician in determining kill over time, and a limited range microorganism species is used under tightly controlled conditions to minimize variability of test results.