565
J. Cosmet. Sci., 75.6, 565–580 (November/December 2024)
*Address all correspondence to Alicia Roso, alicia.roso@airliquide.com
An Innovative Model Based on Wild Type Bacteria
Co-Culture to Identify Cosmetic Ingredients That Respect
the Skin Microbiota
ALICIA ROSO, SOPHIE PÉCASTAINGS, SOPHIE CAMBOS, RICHARD MARTIN,
LAURA BAUCHET, BENOÎT ROUBINET, LUDOVIC LANDEMARRE AND
CHRISTINE GARCIA
Seppic Research and Innovation, La Garenne Colombes, Franc (A.R., S.P., S.C., C.G.)
Mercurialis, Rochecorbon, France (R.M.)
GLYcoDiag, Orléans, France (L.B., B.R., L.L.)
Accepted for publication October 02, 2024.
Synopsis
Human skin is the home of thousands of microorganisms that are well adapted to that hostile environment.
Divesting from the hygienist theory, microorganisms are not considered as potential pathogens anymore, but
as symbionts that must be preserved. With this consideration in mind, cosmetic formulators have sought
ingredients able to preserve and not interfere with cutaneous bacteria. The aim of the present study is to
design a relevant and representative in vitro model of bacteria coculture able to identify ingredients that do not
harm skin microbiota. A protocol was designed to obtain a coculture of the five main bacterial representatives
of the face’s microbiota: Cutibacterium acnes Staphylococcus epidermidis Streptococcus mitis Micrococcus luteus, and
Corynebacterium xerosis, from wild isolates, and in proportions representative of the cheek microbiota. After
8 hours of contact with the test ingredients, bacteria concentrations were measured. A score establishing
the impact of ingredients was implemented, based on the logarithmic reduction of the five species. This
methodology correctly discriminated between known substances with neutral or bactericidal effects. Finally,
four substances used in cosmetic products were evaluated. The proposed model is adapted to screen for
new “microbiota-friendly” ingredients as a first step to design formulations intended to preserve the skin
microbiota.
INTRODUCTION
The human skin represents an interface of 1.5 –2 m2 between the body and its environment.
This complex surface is naturally colonized by a variety of microorganisms that, together,
constitute the skin microbiota. Bacteria are the main representatives (104–106 Colony
Forming Units, or CFU, per cm2), but depending on the area, yeasts and viruses can also
represent a significant proportion of the skin microbiota.1,2 Microorganisms colonizing the
skin, defined as commensals as opposed to transient microorganisms, are very well adapted
J. Cosmet. Sci., 75.6, 565–580 (November/December 2024)
*Address all correspondence to Alicia Roso, alicia.roso@airliquide.com
An Innovative Model Based on Wild Type Bacteria
Co-Culture to Identify Cosmetic Ingredients That Respect
the Skin Microbiota
ALICIA ROSO, SOPHIE PÉCASTAINGS, SOPHIE CAMBOS, RICHARD MARTIN,
LAURA BAUCHET, BENOÎT ROUBINET, LUDOVIC LANDEMARRE AND
CHRISTINE GARCIA
Seppic Research and Innovation, La Garenne Colombes, Franc (A.R., S.P., S.C., C.G.)
Mercurialis, Rochecorbon, France (R.M.)
GLYcoDiag, Orléans, France (L.B., B.R., L.L.)
Accepted for publication October 02, 2024.
Synopsis
Human skin is the home of thousands of microorganisms that are well adapted to that hostile environment.
Divesting from the hygienist theory, microorganisms are not considered as potential pathogens anymore, but
as symbionts that must be preserved. With this consideration in mind, cosmetic formulators have sought
ingredients able to preserve and not interfere with cutaneous bacteria. The aim of the present study is to
design a relevant and representative in vitro model of bacteria coculture able to identify ingredients that do not
harm skin microbiota. A protocol was designed to obtain a coculture of the five main bacterial representatives
of the face’s microbiota: Cutibacterium acnes Staphylococcus epidermidis Streptococcus mitis Micrococcus luteus, and
Corynebacterium xerosis, from wild isolates, and in proportions representative of the cheek microbiota. After
8 hours of contact with the test ingredients, bacteria concentrations were measured. A score establishing
the impact of ingredients was implemented, based on the logarithmic reduction of the five species. This
methodology correctly discriminated between known substances with neutral or bactericidal effects. Finally,
four substances used in cosmetic products were evaluated. The proposed model is adapted to screen for
new “microbiota-friendly” ingredients as a first step to design formulations intended to preserve the skin
microbiota.
INTRODUCTION
The human skin represents an interface of 1.5 –2 m2 between the body and its environment.
This complex surface is naturally colonized by a variety of microorganisms that, together,
constitute the skin microbiota. Bacteria are the main representatives (104–106 Colony
Forming Units, or CFU, per cm2), but depending on the area, yeasts and viruses can also
represent a significant proportion of the skin microbiota.1,2 Microorganisms colonizing the
skin, defined as commensals as opposed to transient microorganisms, are very well adapted