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j. Soc. Cosmet. Chem., 34, 35-39 (January/February 1983) FDA methodology for the microbiological analysis of cosmetics and topical drugs MICHAEL J. PALMIERI, Food and Drug Administration, Department of Health and Human Services, New York Regional Laboratory, 850 Third Avenue, Brooklyn, NY 1 I232. Received June I, 1982. Presented at the SCC-SIM Microbiological Seminar, New York, NY, Dec. 9, I981. Synopsis The microbiological analysis of many cosmetics and topical drugs often presents problems in detecting microbial contaminants. This occurs principally because of poor miscibility of these products with water and because of the presence of preservatives in their formulations. Both improved miscibility of product with medium and neutralization of several preservatives have been achieved by the use of modified letheen medium. A rapid screening test is performed initially to determine if the product is free of contamination. If microbial growth is observed, then plate counts and enrichments are employed to test for Staphylococcus aureus, yeasts, fungi, aerobes, anaerobes, and gram negative bacilli. INTRODUCTION This report deals with the methodology currently employed at the New York Regional Laboratory of the Food and Drug Administration (FDA) for the microbiological analysis of both cosmetic and topical drug preparations. During the period 1979 ß through 1981 approximately two hundred cosmetic and topical drug samples of both domestic and foreign origin were analyzed at the New York Laboratory. The kinds of products tested included skin creams and lotions, shampoos, hair rinses, powders, various eye cosmetics, ophthalmic solutions, and several types of topical ointments and disinfectants. All these product types and especially those with emulsion formulations have been shown at one time or another to contain a wide variety of microorganisms. Sixteen samples (8%) were found to be contaminated with various gram negative bacteria, a group of organisms of special concern because many are potentially pathogenic. Generally, preparations containing 10% or more alcohol, such as after-shave lotions, colognes, and skin refreshners do not present serious microbiological problems. Products with low water activity (aw) such as anhydrous oils, ointments, or petrolatum do not support the growth of large numbers of microorganisms and therefore are also relatively problem-free. 35