THAT UNWANTED COSMETIC INGREDIENT--BACTERIA 139 The bacteria grew plentifully on calcium carbonate-yeast extract agar at room temperature. It did not grow on any of the other media at either temperature. ?11caligenes viscosus is a gram-negative, nonspore forming organism that is found in water and around dairy barns. Once the organism was isolated and its culturing habits known, it was then possible to run through the gamut of preservatives and solve the preservation problem. The manufacturer of the sodium lauryl sulfate was approached and he eventually found this organism in the large storage tank. He believed it got there by taking returned drums of sodium lauryl sulfate and adding them to the storage tank, mixing thoroughly, in order to maintain a uniform product In this way, they believe their entire storage tank became con- taminated. It should be mentioned that this case took place during the latter stages of World War II when sodium lauryl sulfate was rather difficult to obtain and was thus the reason for the manufacturer accepting returned goods. Bacteriological problems in the cosmetic field have become more nu- merous with the extensive use of modern emulsifiers. It does not appear to make too much difference whether they are anionic, cationic or nonionic. The type of bacteria most commonly encountered are: Pseudornonas aeru- ginosa, Pseudomonas fluorescens, .4erobacter aerogenes and the coliform type. I mentioned that I would outline to you the procedure found to be quite efficient in determining whether or not a product is adequately pre- served. These tests require from ten to fourteen days. It should be pointed out, however, that no test has ever been devised that is infallible in respect to showing whether a product is absolutely free from invasion of microbrganisms. The best one can hope for is that his product is adequatel y preserved against most of the common micro Srganisms likely to be encountered. Each cosmetic formulation should be examined separately for its preserva- tion properties. Just because a preservative gives excellent results in one product does not mean that similar results will be obtained in a different formulation. One can liken preservation work to formulating emulsions. If a certain emulsifier, or mixtures of emulsifiers, produces an excellent, stable product, this is no reason why one can expect the same to hold true in other formula- tions. In such instances, various emulsifiers and their combinations are investigated in order to obtain the one best suited for producing the prod- uct desired. The same holds true when it comes to preserving cosmetic products. Bactericidal and bacteriostatic potencies of the preservative must be con- sidered in combination with color, odor, irritation, solubility and compati- bility. If a single preservative does not produce satisfactory results, then

140 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS mixtures of them must be investigated. In fact, most cosmetics today re- quire a mixture of preservatives in order to broaden the antibacterial spec- trum. A product, shown to be adequately preserved, should not be neglected but should be examined periodically for microt3rganisms. I recall one cosmetic manufacturer who had been making an emulsion for quite a few years which appeared satisfactory in every way. For some unknown reason, he subjected it to a bacteriological examination. Imagine his surprise when over 2,000,000 bacteria per gram were found! Consider his con- sternation when control samples a year old, from various plants, also showed this condition! Certainly, he had a stable, marketable product no one knew it was "loaded" with bacteria--not even the manufacturer-- but, what would happen if some consumer got a skin rash and stated that it was caused by the use of this product ? Even if the rash were caused by some other means, the fact that the cosmetic was a "carrier" of bacteria would most likely be sufficient to warrant any judgement in favor of the consumer. The adverse publicity that goes along with such cases should not be con- sidered lightly. Therefore, in order to be certain that your product is ade- quately maintaining its preserved state, examine it periodically for micro- organisms. In order to test the preservation properties of a cosmetic, it is recom- mended that one has available about eight resistant cultures. It is pref- erable that these micro/3rganisms had been isolated from a deteriorated product. It is further recommended that the cultures consist of at least two different strains of Pseudomonas such as aeruginosa and fluorescens derobacter aerogenes the Coliform type a yeast a Penicillium and an d3pergillus. Let us first consider preservation against bacteria: To be sure that the cosmetic product is not highly contaminated with bacteria before one starts the test, it is necessary to make a bacteria count of the product. In making bacteria counts of products that are entirely water-soluble, the regular serial-dilution technique can be followed. However, in examin- ing emulsions such as lotions, creams, pastes, suspensions, powders, cake make-up, etc., it is recommended that from three to six grams of sample be placed in 300 ml. of sterile water contained in a sterile Waring Blendor. The speed of the Blendor can be controlled by a rheostat which is often necessary when handling products that may produce considerable foam. After mixing or dispersing the sample, this dilution can be used for plating and making further serial dilutions. One will also find this technique most helpful in the examination of water-in-oil emulsions.