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Cosmetics

Microbial Contamination

Risk factors for Skin Infection

James Leyden

Emeritus Prof. U.of Penna.

Skin Defense Mechanisms

� Stratum corneum physical barrier

� Straum corneum & surface lipids

� Innate Immune response Toll like Receptors

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HYDROPHILIC – AQUEOUS ENVIRONMENT

INTERCELLULARSPACE

LIPIDBILAYERS

PLASMAMEMBRANE FATTY ACID

CHOLESTEROL SULFATE

CHOLESTEROL

GLUCOSYLCERAMIDE

CERAMIDE

P

NP

P

P–Polar Region of BilayerNP–Non-Polar Region of Bilayer

Intracellular lipidsIntracellular lipids

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PROTECTIVE FUNCTIONS OF

STRATUM CORNEUM

� MECHANICAL (External Trauma)

� ANTIMICROBIAL

� ANTIOXIDANT

� CYTOKINE ACTIVATION

� UVL

� CHEMICAL DEFENSE

Skin Microflora

� 16 S rRna technology reconfirms the

enormous diversity of microorganisms

� Resident Transient Resident Transients

� Resident flora varies by site includes

Coagulase negative Cocci, Micrococci,

Diphtheroids, Propionibacteria,

yeasts,fungi

Experimental Bacterial Inoculation

� In early & mid 1970s, our group conducted

numerous studies relevant to the question of the

potential risk of bacterial contaminated

cosmetics and skin infection

Effect of resident flora on wounds

Survival of pathogens on normal skin

Effects of pathogens on damaged skin

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Inoculation Studies

� Survival of heavy inoculum of various organisms

on hands Survival quantified by glove juice &

image analysis of density by image analysis

� Inoculation of resident organisms on

experimental wounds with occlusion

� Inoculation of S.aureus. S.pyogenes,

Pseudomonas on intact and damaged skin with

occlusion

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Resident Flora

� Superficial wounds made on volar forearm

inoculated, covered with an occlusive dressing

� Quantitative cultures and wound healing

measurements

� S.epidermidis, S.hominis. S.capitis,

M.luteus,corynefomr diphtheroids

� No host reaction no effect on healing

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S. Aureus

� Enormous variability in potential pathogenicity

for skin

� In tropical environments can be part of resident

flora in the perineum

� Skin of those with atopic dermatitis heavily

colonized

� HIV patients heavily colonized

� Toxin producing strains damage skin & evoke

host response

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S. Pyogenes

� Inoculation on normal skin, even under

occlusive dressing, leads to rapid death due to

inhibitory effect of fatty acids in skin lipid film

� Inoculation on scarified skin results in brisk host

response

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Pseudomonas

� P.aerugenosa and other GNB are highly

pathogenic in burn victims Diaper area heavily

contaminated without infection as is often seen

in skin ulcers

� Studies with the Special Pathogen Division of

the CDC showed pseudomonas not harmful to

normal skin and induces mild reaction on

damaged skin

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Conclusions

� Our studies show no adverse effects of resident

coagulase negative cocci

� S.aureus strains vary in their potential for

adverse effects on skin

� Pseudomonas is not harmful to normal skin but

can elicit a mild response on damaged skin

� Current guidelines in the cosmetic & toiletry

industries for determining the potential risk for

bacterial contamination are clearly adequate

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