Pseudomonas–The Nemesis of the Cosmetic Industry

By: Donald Orth, PhD

Posted: September 24, 2009

Several microorganisms have attained special significance in the cosmetic industry, either because they occur frequently in the manufacturing plant as house organisms and cause contamination of products, or because they create undesirable conditions when they cause or exacerbate skin disorders (e.g., facial blemishes, axillary odor, athlete's foot, etc.) or cause health hazards (e.g., infections, keratitis, etc.) when products containing them are used. Microorganisms are ubiquitous, and sooner or later they find their way into raw materials, production equipment, and even finished products (especially when the preservative systems are inadequate). Thus, it is likely that every cosmetic and drug manufacturer who has been in the business for a few years has had some type of microbiological problem. And, if one were to conduct a survey to see which microorganism caused the most problems, they would probably say Pseudomonas!

Members of the genus Pseudomonas are Gram-negative, motile, aerobic rods that generally are oxidase positive. Some pseudomonads produce water-soluble pigments. These bacteria occur widely in nature. They are found in soil and water and on plants, and may be associated with animals. Pseudomonas aeruginosa frequently is present in small numbers in the normal microflora of the gastrointestinal (GI) tract and on the skin of humans (as transient microflora). P. aeruginosa is the most virulent opportunistic pathogen of the genus Pseudomonas. P. aeruginosa is an amazing microorganism because it is quite innocuous in most environments—but it also can cause severe and life-threatening infections (especially in immunocompromised patients) and it can be a house organism that is very difficult to eradicate from manufacturing plants.

It is well known that microbial contamination problems encountered during manufacturing often may be traced to the microbial quality of the raw materials. Pseudomonads can survive and grow in DI water. Contaminated DI water may be the source of microbial contamination if it is used for the final rinse of equipment that has been cleaned and sanitized, and it may be the source of contamination for finished products.

Microorganisms have survival strategies and virulence factors that enable them to adapt to changing environments and to be more aggressive pathogens. Survival strategies become virulence factors during infections, so they are the morphological features and physiological characteristics that enable microorganisms to be pathogenic—to establish infections, be invasive, produce toxins, avoid immune clearance mechanisms, and become drug resistant.

P. aeruginosa is the most virulent opportunistic pathogen of the genus Pseudomonas. Pathogenesis of this bacterium is mediated by a suite of cell-associated and secreted virulence factors including flagella, lipopolysaccharide (LPS) that suppresses host immune responses and aids in establishing persistent infections, proteolytic enzymes (elastase and protease) that destroy the integrity of host tissues, low molecular weight toxins that interfere with cell metabolism and protein synthesis, active efflux pumps that expel antimicrobial compounds, cell-to-cell signaling (i.e., quorum sensing), and biofilms which help protect the bacteria. Some of the same mechanisms that make pseudomonads difficult to treat also make them difficult to eradicate from manufacturing plants.