594 JOURNAL OF COSMETIC SCIENCE
genus and species levels to define a putative bacterial signature for SS, as this could help to
better understand and eventually improve this skin condition.
Unlike Keum’s study13 that showed no changes in Cutibacterium and Staphylococcus genus
levels, or Jarrin et al.16 who observed an increase in Cutibacterium and a nonsignificant
decrease in Staphylococcus, we demonstrated an increase in Cutibacterium and a decrease in
Staphylococcus genus abundance between cohorts. This could be explained by a difference
in cohort (location, size, and age classes) and analytical methods used for sequencing. Our
data more closely matched with Filaire et al.,20 who showed that in SS there was an increase
in Actinobacteria (phylum composed essentially by Cutibacterium and Corynebacterium
genera) and a decrease in Firmicutes (phylum composed among others by the Staphylococcus
genus). Although not significant in relative frequency (p 0.05), Cutibacterium, Paracoccus,
and Corynebacterium were also found increased by Bai et al.,15 whereas Staphylococcus were
found decreased. Interestingly, Zheng et al.14 also showed that Staphylococci, particularly
S. epidermidis, significantly decreased in SS (p =0.028). Moreover, as S. epidermidis decreased
gradually with the degree of skin sensitivity, they indicated a correlation between skin
microbiome changes and female LAST score ≥3.
To complete our analysis, we observed no change in abundance of Corynebacterium and a
decrease in Staphylococcus in SS subjects. This partially aligns with the findings of Bai’s
study,15 which indicated a trend towards an increase in Corynebacterium and a decrease in
Staphylococcus, or Jarrin’s study,16 who reported a significant increase in Corynebacterium, but
not significant decrease in Staphylococcus. As observed by Jarrin et al.,16 we also observed
an increase in Kocuria, Micrococcus, and Lactococcus genera (data not shown). However,
we also observed contrasting results compared to them for Cutibacterium, Bacillus, and
Lawsonella, whose abundance tend to increase in our SS subjects, whereas they indicated
that Lactobacillus was decreased (data not shown). This could be explained by the difference
in the cohort ages (as Jarrin et al. focused on 20–50 year old panelists, while we analyzed
18–77 year old panelists) and/or the analytical method (targeted V3-V4 16S rRNA variable
regions versus V1-V9).
Our results are also partly in accordance with Hillion et al.12 as we observed in SS an increase
in the abundance of Corynebacterium and Brevibacterium (data not shown) and a decrease in
Staphylococcus. Having a mixed cohort, we also observed an increase in Micrococcus that they
only observed in male SS.
Taken all together, these combined results seem to demonstrate a core group of genera
that were increased in SS including Corynebacterium, Kocuria, Micrococcus, Lactococcus, and
Brevibacterium, whereas Staphylococcus was decreased. Additional, large studies on other bacteria
such as Cutibacterium, Bacillus, or Acinetobacter would help to further refine their status in SS.
Going deeper to the strain level provides additional insight as it more precisely highlights
the changes within a genus. For Corynebacteria, we observed a 1.6-fold increase in
Corynebacterium kroppenstedtii, already the most abundant species in NS. Little is known
about the Corynebacteria genus members contribution in SS, however an increase in
Corynebacterium kroppenstedtii was previously correlated to skin redness showing that this
bacterium could be involved in both the redness and sensitivity of the skin.20 Ridaura et al.
also showed in mice with high-fat diets that certain Corynebacteria, such as Corynebacterium
accolens, could promote inflammation in an IL-23 dependent manner.21 Corynebacterium and
particularly Corynebacterium kroppenstedtii could thus be considered as a way for cosmetic
care products to address SS.

595 Specificities of Microbiota From Sensitive Skin
Recent research indicates that the bacterial diversity and the relative abundance of different
microbes present on and in the skin may contribute to skin barrier dysfunction.22,23 In this
study, we have shown in the SS that the Staphylococcus genus level was decreased, but that
a 2.8-fold increase of S. aureus was observed with a correlated decrease of S. epidermidis,
S. capitis, S. equorum. S. hominis, or S. saprophyticus for the more abundant. Therefore, it seems
important to pay attention to S. aureus, S. epidermidis, S. hominis, S. capitis, or other coagulase
negative Staphylococci counterparts to help improve SS condition. Firstly, it was shown that a
S. epidermidis decrease correlates to high LAST score.14 Secondly, S. aureus secretes multiple
virulence factors known to contribute to skin barrier dysfunction (multiple metalloproteases
disrupting proteolytic balance in the skin).24 Finally, S. epidermidis and hominis produce
strain-specific, highly potent antimicrobial peptides (AMPs) that selectively kill S. aureus
and synergize with the human AMP LL-37,25 and some S. capitis also express strong
antibacterial activity against a range of Gram-positive species, most notably including
S. aureus strains with resistance to methicillin (MRSA) and strains with intermediate
resistance to vancomycin (VISA).26
After the analysis of the metagenome between the two cohorts, we used DBMT to isolate
bacterial species in culture from NS and SS and create a bacterial collection from these
clinical isolates. We previously observed that this technology was particularly suitable for
isolating bacteria that are known to be difficult to isolate and cultivate. Here we isolated
hundreds of species from each cohort and selected 31 strains as a representative for each.
On these 62 strains, we evaluated the effect of some preselected ingredients on the growth
profile of the selected species from both collections. Due to different bacterial growth
conditions and responsiveness to active ingredients, we monitored the growth over 72 hours,
with a dose range of the active ingredients. This strategy could be used for identifying
prebiotic ingredients for specific species of interest. For example, some species have been
shown to decrease with age and could therefore be used to restore a growth pattern closer
to a younger skin profile. For SS, the same methodology could be applied to compensate
the switch in abundance observed in SS at least for the common species highlighted and
including, if feasible, the less common microbe genera described. This system can also
be used to identify ingredients with minimal effects, those that can also be said to be
“microbiome friendly.”
Finally, when studying the potential damage induced on keratinocytes by C. acnes, more
abundant species found in the two cohorts of this study were evidenced. We determined
that C. acnes strains isolated from SS decreased the viability of keratinocytes (SS4 and SS8)
while two strongly induced IL-8 release by keratinocytes (SS4 and SS7) when compared to
the effect the species from NS. Consequently, in addition to showing an increase of C. acnes
in the SS, we also demonstrated that some specific strains present on the SS were more
detrimental to keratinocytes and could contribute to localized inflammation. This method
and its findings could be compared with those of Lu et al.,17 who examined the capacity
of standard S. epidermidis (ATCC12228) and S. aureus (USA 800) species to stimulate IL-8
secretion in keratinocytes, comparing them to S. epidermidis, S. aureus, S. capitis, and M.
luteus species isolated from a panelist with SS. They observed a higher IL-8 induction with
S. aureus when from SS, and also a very high induction with S. capitis and M. luteus from
SS. Altogether these results highlight the importance of isolating species specific to SS in
an effort to later search for ingredients that could not only help to compensate the shifts in
prevalence and/or abundance of these species between NS skin and SS, but also to regulate
their related virulence potential.