j. Soc. Cosmet. Chem., 31, 19-28 (January/February 1980) Experimental inoculation of Pseudomonas aeruginosa and Pseudomonas cepaciae on human skin JAMESJ. LEYDEN, REBECCA STEWART, Duhring Laboratories, Department of Dermatology, University of Pennsylvania, Suite 203, 3500 Market Street, Philadelphia, PA 19104 and ALBERT M. KLIGMAN Duhring Laboratories, Department of Dermatology, University of Pennsylvania, Suite 203, 3500 Market Street, Philadelphia, PA 19104 and Simon Greenberg Foundation, Suite 226, 3401 Market Street, Philadelphia, PA 19104. Received June 14, •979. Synopsis Thirteen strains of PSEUDOMONAS AERUGINOSA and three strains of PSEUDOMONAS CEPACIAE were inoculated onto intact HUMAN SKIN of volunteers. INOCULATION on normal skin failed to produce lesions despite high numbers of Pseudomonas (10 6) for aS long as 7 days) Use of superhydration type of dressings which damages the stratum comeurn in conjunction with inoculation of Pseudomonas resulted in lesions consisting of papules and pustules. No difference were found among the sixteen strains. Inoculation into superficial scarifications resulted in papulovesicular transient reactions as Pseudomonas strains failed to survive. Dose response studies indicated that an inoculum in excess of 105 organisms is required to induce a lesion on scarified skin. INTRODUCTION Pseudomonas aeruginosa by any means of reckoning is a truly remarkable organism. It is ubiquitous and can grow in swamps, soil, sewerage, jet fuel, sinks, and antiseptic solutions, on flowers and vegetables, and even in distilled water (1). P. aeruginosa is a major cause of spoilage of various products ranging from cosmetics to refrigerated meats and fowl (2,3). Its omnipresence and growth potential stands in contrast to the relative rarity with which it causes human disease. Considering the ever present exposure to this organism, skin infections are uncommon and only a tiny fraction of those caused by Staphylococcus aureus and Streptococcus pyogenes. Well defined superficial infections in humans include the "green nail" syndrome with paronychia (4), otitis externa (5), and the erosive form of athletes foot (6,7). Thus for the most part P. aeruginosa quietly shares the ecosystem and healthy persons have little to fear despite intense exposure. On the other hand, Pseudomonas is not always so innocent. In third degree burns, infection with P. aeruginosa all too frequently results in death. In immunosuppressed patients and in those in whom the normal defenses are exhausted, e.g., in the final stages of malignancy, the debilitated elderly, the surgically traumatized, Pseudomonas septicemia and its cutaneous manifestation, ecthyma gangrenosum, are rightfully feared 19

20 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (8). In the presence of Pseudomonas, trauma to a tissue such as the cornea may result in severe inflammation and even blindness. Though rare, accidental scratching of the cornea during application of Pseudomonas-contaminated mascarea has eventuated in loss of vision (9). Another example of the ability of Pseudomonas to attack the compromised host was seen in an epidemic of secondary skin infections which occurred on a ward in which Pseudomonas-contaminated steroid creams were used in common (10). The perception of hazard from Pseudomonas infection largely depends on one's position in the clinical theater. In outpatient practice, the organism is taken rather lightly, for the usual presentations such as ear and foot infections are highly localized and manageable by topical therapy. Even large numbers of Pseudomonas in a damaged site are not an immediate call for action. Stasis ulcers, for example, are frequently colonized by Pseudomonas and yet there is no good evidence that their presence or absence materially affects the rate of healing. On the other hand, the hospital-based internist and surgeon maintains a stout vigilance against superinfections with this organism in very sick patients. In sum, P. aeruginosa appears to be an opportunistic organism of relatively low virulence which has the capacity to become invasive when prior injury has depleted normal defenses. Recently, reports have appeared which are inconsistent with this view. These state that certain strains of Pseudomonas can induce skin reactions in normal persons even after brief contact (11,12,13). The reports concern individuals who swam in heated pools which are apparently insufficiently chlorinated, permitting the water to become contaminated with Pseudomonas. The manifestations were limited to the skin and consisted of widespread papulovesicular lesions and folliculitis. Three well-studied epidemics have brought to light 69 individuals with extensive eruptions. While the skin was cultured in only six cases, the organism recovered was the very strain that had been isolated from the pool. Patients and a few physicians thought the lesions were insect bites. The attack rate in the 3 outbreaks was 6.5, 53 and 85% respectively. It is noteworthy that rashes were more frequent in those who repeatedly used the pools. These reports stimulated us to review our own published experimental studies involving this organism. When the legs of elderly subjects were occluded for a week or more under an impermeable plastic film, the skin remained healthy. On the other hand, when pads soaked in tap water were applied under impermeable dressings a vesiculo-pustular rash developed in 26 of 32 subjects (14). Epidermal necrosis and hemorrhage were noted histologically, signifying severe damage. In each instance high densities of P. aeruginosa varying from 106 to 107 organisms/cm • were recovered from those with eruptions. Organisms were not demonstrated with the living tissue. Presumably the source of the organism was city tap water although this was not formally documented. Superhydration with wet pads enabled a great multiplication to take place. Also, it is known that excessive hydration damages the horny barrier layer considerably increasing its permeability and weakening the strength. The lesions were interpreted as toxic reactions to products, most likely proteolytic enzymes, which had been released from a huge population of Pseudomonas growing on the water-logged surface. The severity of the exposure under those artificial circumstances in no way resembles swimming briefly in a pool containing low densities of Pseudomonas. In another study, Singh applied a suspension of P. aeruginosa under occlusion to human skin for 3-6 days (d) (15). Although dense populations were created, ranging from thousands to many millions/cm •, the skin remained essentially normal. However,