583 Specificities of Microbiota From Sensitive Skin
secretion, and facial skin surface morphology were evaluated in parallel to 16S rRNA
sequencing. No change in diversity was observed for SS and NS face skin. In the three
most common microbiota genera, including Cutibacterium, Paracoccus, and Corynebacterium,
there was no significant difference in the relative frequency among the SS and NS groups.
Nevertheless, at the genus level the authors found that in the SS group a significantly
higher frequency of rare bacteria such as Acidaminococcus, Alloiococcus, Fimbriimonas,
Pseudoclavibacter, Reyranella, and Roseococcus, but a lower frequency of Bradyrhizobium.
Spearman correlation analysis showed correlation between the microbiota genera and skin
physiological parameters. However, they found no bacterial genus with strong association
with skin physiological parameters.
A study on Caucasian women (cheek, SS evaluation using capsaicin test (61 NS 23–50
years old, 23 NS 51–69 years old, and 44 SS 20–50 years old) likewise did not show
a difference in diversity. Nevertheless, SS compared to NS with the same age class was
reported here to display a specific microbiota profile with a significant decrease in SS in
Cutibacterium, Lawsonella, and Bacillus (nonsignificant decrease for Staphylococcus), and an
increase in Corynebacerium, Snodgrassela, Kocuria, and Micrococcus.16
Finally, in 2024, Lu et al. performed a study on 10 panelists (cheek, 22–35 years old,
LAST-based recruitment) using a 2bRAD-M sequencing method enabling accurate
characterization of the low-biomass microbiome at species level. They showed in the
SS group a decrease of alpha diversity and an increase of abundance in the 3 top genera
Cutibacterium, Corynebacterium, and Staphylococcus. Among Staphylococci, S. epidermidis was
the more abundant and increased by 1.34-fold, whereas less abundant S. aureus was
the most increased (2.98-fold). They also observed that the relative abundance of rare
bacteria such as Dermabacter hominis and Chryseobacterium was significantly increased,
whereas those of Neisseria and Streptococcus decreased. Advantageously, Staphylococci
(S. epidermidis, S. capitis, and S. aureus) and Micrococcus luteus from a panelist with SS
were extracted and compared to standard S. epidermidis and aureus for their ability to
induce Interleukin-8 (IL-8) in keratinocytes. Interestingly, S. capitis and M. luteus from
the panelist with SS significantly promoted more IL-8 expression than S. epidermidis and
S. aureus.17
In this study, our goal was to first compare the composition of the skin microbiota of
individuals with NS and SS using the entire 16S rRNA gene sequencing from PacBio
technology to obtain unprecedented taxonomic resolution of the microorganisms present.
However, at the same time, we evaluated for the first time droplet-based microfluidic
technology (DBMT) to create a collection of specific bacterial species isolated from
individuals with SS and NS. DBMT was chosen as this microbiome-on-a-chip high-
throughput technology can generate more than 100 million parallel picoliter-sized droplets,
allowing the isolation of live bacterial species that grow to clonal populations at a much
higher diversity compared to standard microbiology methods when using specific culture
media. In addition, the picoliter-sized droplets containing bacteria can be isolated drop
by drop for subsequent bacterial clones’ characterization and further cosmetic ingredient
testing. The bacterial collection was used here to study the impact on bacterial growth
of cosmetic ingredients. Isolates of C. acnes from both the NS and SS collections were
also compared for their potential to stimulate the proinflammatory cytokine IL-8 in
keratinocytes with the final aim to build a screening tool using a set of bacteria previously
shown to be modulated in SS and to have impact on SS features.

584 JOURNAL OF COSMETIC SCIENCE
MATERIALS AND METHODS
RECRUITMENT OF PARTICIPANTS AND SAMPLING PROTOCOL
The study was conducted in accordance with the Declaration of Helsinki (statement of
ethical principles applicable to medical research involving human beings, including research
on human biological material and identifiable data) and informed consent was obtained
from all subjects involved in the study. Seventy-eight volunteers assessed by dermatologists
were found to have healthy skin (free of eczema, psoriasis, wounds, and inflammatory
scaring) and were enrolled in this study. We recruited males and females, aged 18–77 years
old, and having the skin phototype ranging from 1–5. Among the 73 volunteers on which
the analysis was completed, 30 reported having thin and sensitive skin, and were tested
for their hypersensitivity to heat prior to sampling. More precisely, recruited panelists of
the sensitive skin cohort had an electrodermal response evaluated at 155% after a heating
stimulation on the cheeks versus before (using skin conductance response rate measured
with a Galvanic Skin Response electrode).
The skin site investigated in this study was the face. Participants were asked not to wash
their face 24 for hours prior to sample collection, as well as not to apply any cosmetics
during this time frame. A cotton swab immersed in 1.5 mL of skin sampling buffer (10%
glycerol, 0.1% Tween80 in 1× phosphate buffer saline) was used for sampling. An area of
4 cm2 on the cheek was vigorously rubbed with the cotton swab for 30 seconds. Swabs
were then vortexed for 30 seconds at maximum speed in a 1.5 mL microtube to resuspend
biological matter in solution. They were squeezed to maximize the volume of SSB (Single-
Stranded Binding buffer Thermo Fisher Scientific, Massachusetts, United States) in the
microtube by centrifugation. The samples were concentrated in 400 microliters (µL) of 1×
phosphate buffer saline and stored at −80°C until DNA extraction.
DNA EXTRACTION
DNA was extracted using the kit Zymo BIOMICS™ DNA miniprep (D4300, Zymo
Research, Irvine, CA, USA) following manufacturer recommendations including a
mechanical lysis step with BashingBead™ Lysis tube. Blank extractions without swab
samples were also performed to check for potential contamination. The final DNA was
eluted in 50 µL of nuclease-free water. DNA samples were kept at −80°C until bacterial
quantification.
DNA QUANTIFICATION
These TaqMan™ probe-based quantitative polymerase chain reaction (qPCR) assay
(Thermo Fisher Scientific) was used to measure the bacterial concentration of the samples.
The TaqMan™ probes have a 5′ fluorescent reporter dye and a 3′ quencher dye. These
probes are target-specific, and only bind to the DNA sequence of interest downstream
of one of the primers during the annealing step. A culture of Escherichia coli (E. coli) was
grown overnight at 37°C in brain heart infusion (BHI) medium, which was followed by
a DNA extraction. The eluted DNA was quantified using Qubit™ dsDNA HS assay kit
(Thermo Fisher Scientific) following manufacturer recommendations using 5 µL of E. coli
DNA solution to generate standard curves.