[Microbiological purity of pharmaceutical preparation. Part 1: External remedies; and effects of type of cream, container, storage, temperature and application (author's transl)]. / Mikorbiologische Reinheit der Arzneizubereitungen.

A fractional factorial experiment of the 2n type was carried out, to follow the effects of eight factors affecting simultaneously the microbiological purity of creams (Oleocremor leniens, Hydrocremor stearini) during the manufacturer-consumer chain. The effects of these factors (antibacterial substances, container (collapsible tube, pot), type of cream, storage (open, closed), number of takeouts, manner of taking-out (spatula, finger), temperature of storage, consumer (dermatological clinic, household) and interactive and interdependent. The microbiological purity of the creams is mostly impaired by the number of take-outs and the manner of taking-out. Collapsible tubes and, perhaps even better, one-dose packings are considered a solution of this problem. It is recommended to investigate creams individually with reference to their composition and structure, contents of antibacterial substances, technology and application. The tentative specification for the microbiological purity criteria of ointments and creams, designed for the Czechoslovak Pharmacopoeia, 4th Edition, is acceptable.

[Microbiological purity of pharmaceutical preparation. Part 2: External remedies; the effects of antimicrobial agents in various contaminated creams (author's transl)]. / Mikrobiologische reinheit der arzneizubereitungen. teil 2: externa; wirkung antimikrobieller stoffe in verschiedenen kontaminierten cremetypen.

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.