[Microbiological purity of pharmaceutical preparation. Part 2: External remedies; the effects of antimicrobial agents in various contaminated creams (author's transl)].

To study the efficiency of antimicrobial agents in contaminated creams, a complete four-factor trial was performed with Oleocremor leniens, Oleocremor syndermani and Hydrocremor stearini. These creams were prepared with and without the addition of antimicrobial agents (parabene combination, potassium sorbate), contaminated with 5 genera of micro-organisms and bacteriologically examined immediately after preparation and after storage for 14 and 28 d, respectively. It was found that all four factors considered in this trial (type of cream, type of antimicrobial agent, genus of microorganism, time) are interdependent. The efficiency of the antimicrobial agents depends above all upon the type of cream (which acts on the availability of the antimicrobial agents) and upon the micro-organisms. The global recommendation of anti-microbial agents is unsuitable. The test organisms and the test methods as well as the evaluation of their results should be standardized.