10.5826/dpc.1204a191
Background: Hidradenitis suppurativa (HS) is a systemic inflammatory disease that extends beyond the skin. The role of gut microbiome alterations in the pathogenesis of inflammatory and autoimmune disorders is remarkable.Objective: Based on the hypothesis that dysbiosis in the gut microbiome may be a trigger for systemic inflammation in the pathogenesis of HS, the aim of this study was to investigate whether the gut microbiome is altered in HS patients comparing with healthy subjects.Methods: In present case-control study, fecal samples from 15 patients with HS and 15 age- and sex-matched healthy individuals were collected and analyzed using 16S rRNA-based metagenomic analysis. The V3 and V4-hypervariable regions of 16S rDNA gene were amplified from all samples and sequenced by the Illumina MiSeq platform. Bioinformatic analyzes were performed in QIIME2. Results: Shannon alpha diversity index showed significantly reduced diversity in HS patients (P = 0.048). Bray-Curtis Dissimilarity and Jaccard Distance revealed that the gut microbial composition of HS patients was significantly distinctive from that of controls (P = 0.01 and P = 0.007, respectively). The relative abundance of unclassified Clostridiales, unclassified Firmicutes and Fusicatenibacter in HS was significantly lower than that in controls (P = 0.005,&nbsp; P = 0.029, and P = 0.046, respectively).Conclusion: This study indicated that significant alterations in gut microbiota of HS patients could play a critical role in the pathogenesis of HS and might be a trigger for systemic inflammation. Increased understanding the pathogenesis of HS will shed light on the new potential therapeutic targets and novel treatment options.
text/xml
2160-9381
2257
en
Nilgün Atakan
https://creativecommons.org/licenses/by-nc/4.0
Dermatology Practical & Conceptual
gut microbiome
Alterations of the human gut microbiome in patients with hidradenitis suppurativa: a case-control study and review of the literature: Gut microbiome in hidradenitis suppurativa
Text.Serial.Journal
https://dpcj.org/index.php/dpc
Original Article
2022-10-31
2021-12-15
2022-10-31
2022-12-02
e2022191
Dermatol Pract Concept
Background: Hidradenitis suppurativa (HS) is a systemic inflammatory disease that extends beyond the skin. The role of gut microbiome alterations in the pathogenesis of inflammatory and autoimmune disorders is remarkable.Objective: Based on the hypothesis that dysbiosis in the gut microbiome may be a trigger for systemic inflammation in the pathogenesis of HS, the aim of this study was to investigate whether the gut microbiome is altered in HS patients comparing with healthy subjects.Methods: In present case-control study, fecal samples from 15 patients with HS and 15 age- and sex-matched healthy individuals were collected and analyzed using 16S rRNA-based metagenomic analysis. The V3 and V4-hypervariable regions of 16S rDNA gene were amplified from all samples and sequenced by the Illumina MiSeq platform. Bioinformatic analyzes were performed in QIIME2. Results: Shannon alpha diversity index showed significantly reduced diversity in HS patients (P = 0.048). Bray-Curtis Dissimilarity and Jaccard Distance revealed that the gut microbial composition of HS patients was significantly distinctive from that of controls (P = 0.01 and P = 0.007, respectively). The relative abundance of unclassified Clostridiales, unclassified Firmicutes and Fusicatenibacter in HS was significantly lower than that in controls (P = 0.005,&nbsp; P = 0.029, and P = 0.046, respectively).Conclusion: This study indicated that significant alterations in gut microbiota of HS patients could play a critical role in the pathogenesis of HS and might be a trigger for systemic inflammation. Increased understanding the pathogenesis of HS will shed light on the new potential therapeutic targets and novel treatment options.
Nilgün Atakan
2022/10/31
10.5826/dpc.1204a191
e2022191
Hacettepe University, Department of Dermatology and Venereology, Ankara, Turkey
2160-9381
gut microbiome
en
e2022191
Prakash A, Peters BA, Cobbs E, et al. Tobacco Smoking and the Fecal Microbiome in a Large, Multi-ethnic Cohort. Cancer Epidemiol Biomarkers Prev. 2021;30(7):1328-1335. doi:10.1158/1055-9965.EPI-20-1417
Alterations of the human gut microbiome in patients with hidradenitis suppurativa: a case-control study and review of the literature: Gut microbiome in hidradenitis suppurativa
https://dpcj.org/index.php/dpc/article/download/2257/1784
       Alterations of the Human Gut Microbiome
      in Patients With Hidradenitis Suppurativa: A
    Case-control Study and Review of the Literature
                         Neslihan Demirel Öğüt1, Gülşen Hasçelik2, Nilgün Atakan1


1 Hacettepe University, Department of Dermatology and Venereology, Ankara, Turkey
2 Hacettepe University, Department of Medical Microbiology, Ankara, Turkey



Key words: hidradenitis suppurativa, inflammatory skin disorders, gut microbiome, pathogenesis
Citation: Demirel Öğüt N, Hasçelik G, Atakan N. Alterations of the human gut microbiome in patients with hidradenitis suppurativa:
a case-control study and review of the literature. Dermatol Pract Concept. 2022;12(4):e2022191. DOI: https://doi.org/10.5826/
dpc.1204a191
Accepted: March 14, 2022; Published: October 2022
Copyright: ©2022 Demirel Öğüt et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-
NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use,
distribution, and reproduction in any medium, provided the original authors and source are credited.
Funding: This study was supported by the Turkish Society of Dermatology (Grant 2018/179) and Hacettepe Dermatology Association
(Grant 2019/1).
Competing interests: None.
Authorship: All authors have contributed significantly to this publication.
Corresponding author: Neslihan Demirel Öğüt, MD, Uşak University, Department of Dermatology and Venereology, Uşak, Turkey, Phone:
+90 276 224 00 00, E-mail: neslihandemirel459@gmail.com




  ABSTRACT             Introduction: Hidradenitis suppurativa (HS) is a chronic and systemic inflammatory disease that
                       extends beyond the skin. The role of gut microbiome (GM) alterations in the pathogenesis of inflam-
                       matory and autoimmune disorders is remarkable.
                       Objectives: Based on the hypothesis that dysbiosis in the GM may trigger systemic inflammation
                       in the pathogenesis of HS, this study aimed to investigate whether the GM is altered in HS patients
                       compared with healthy subjects.
                       Methods: In the present case-control study, fecal samples from 15 patients with HS and 15 age- and
                       sex-matched healthy individuals were collected and analyzed using 16S rRNA-based metagenomic
                       analysis, New Generation Sequencing (NGS). The V3 and V4-hypervariable regions of the bacterial
                       16S rDNA gene were amplified from all samples and sequenced by the Illumina MiSeq platform. Bio-
                       informatics analyses were performed in QIIME2.
                       Results: Shannon alpha diversity index showed significantly reduced diversity in HS patients (P =
                       0.048). Bray-Curtis Dissimilarity and Jaccard Distance revealed that the gut microbial composition of
                       HS patients was significantly distinctive from that of controls (P = 0.01 and P = 0.007, respectively).
                       The relative abundance of unclassified Clostridiales, unclassified Firmicutes, and Fusicatenibacter in
                       HS was significantly lower than that in controls (P = 0.005, P = 0.029, and P = 0.046, respectively).
                       Conclusions: This study indicated that significant alterations in the GM of HS patients could play a critical
                       role in the pathogenesis of HS and might be a trigger for systemic inflammation. Increased understanding of
                       the pathogenesis of HS will shed light on the new potential therapeutic targets and novel treatment options.



Original Article | Dermatol Pract Concept. 2022;12(4):e2022191                                                                         1
Introduction                                                     any infections, previous gastrointestinal tract surgery, and
                                                                 malignancy were included in the study. The diagnosis of
Hidradenitis suppurativa (HS) significantly impacts patients     HS was based on clinical criteria [15]. The severity of the
quality of life with its chronic and relapsing course and sub-   disease was evaluated by Hurley Stage, modified Sartorius
optimal response to therapy [1]. The etiopathogenesis of         Score, and International Hidradenitis Suppurativa Severity
the disease has not been elucidated yet. However, it is clear    Score System (IHS4) [16]. Patients and healthy controls were
that HS is not simply an inflammatory skin disorder, but a       not given dietary restrictions before stool sampling. In order
systemic inflammatory disorder [2]. Its associations with        to assess the possible effect of obesity, smoking status, and
inflammatory and autoinflammatory disorders, increased           current treatment on gut microbiome profile, fecal samples
levels of inflammatory cytokines in sera of patients, and        of HS patients were stratified by body mass index (BMI),
γ-secretase complex mutations leading to impaired notch          smoking, and current treatment status.
signaling pathway may suggest a systemic inflammation that          This study was approved by the Hacettepe Univer-
distant skin sites might trigger [3].                            sity Non-Interventional Clinical Research Ethics Board
    Recently, a term called “gut-skin axis” has been intro-      [24.07.2018, GO 18/62925]. Written informed consent was
duced and highlighted a potential link between the gut           obtained from all subjects prior to their enrollment.
microbiome and the skin through complex immune mecha-
nisms [4]. The gut microbiome refers to the whole genome of      Fecal Sample Collection
the residential microbial community in the human intestine.      Fecal samples from all participants were collected in sterile
An altered gut microbiome is involved in the development         containers. Then, all samples were transferred to a freezer
of multiple immune-mediated and inflammatory disorders,          within 60 minutes of collection and stored at −80°C until
especially of inflammatory bowel diseases (IBD), by disrupt-     analyzed with New Generation Sequencing (NGS).
ing the balance between pro-inflammatory and anti-inflam-
matory/regulatory immune cells [5,6]. Many studies have          DNA Extraction
revealed dysbiosis, alterations in the gut microbiome, in in-    Total DNA extraction from 30 fecal samples was performed
flammatory and autoimmune skin disorders such as acne,           using The Biospeedy® DNA Isolation Kit (Bioeksen R&D
rosacea, atopic dermatitis, and psoriasis [7-10]. However,       Technologies) according to the manufacturer instructions.
studies exploring the gut microbiome alterations in patients     Feces (200 mg) was transferred to 300 µL of buffer (200
with HS are scarce in the literature [11-14].                    mM Tris-HCl, pH 8.0; 20 mM EDTA; 10% Triton X-100)
                                                                 and 0.1-mm glass bead containing tubes and homogenized
Objectives                                                       at 6000 rpm for 1 min. 0.1 µL lysozyme (200 μg/μL) was
                                                                 added to the sample and incubated at 37°C for 15 minutes.
In the present study, we hypothesize that the gut microbiome     Subsequently, 250 µl lysis buffer (0.5 μg /μl Proteinase K,
of patients with HS is different from that of healthy people.    5% Tween® 20, 3M Guanidinium thiocyanate, 20 mM
Therefore, in this study, we aimed (1) to evaluate the gut mi-   Tris-HCl, pH 8.0) was added to the sample and incubated
crobiome of patients with HS, (2) to compare it with healthy     at 70°C for 15 minutes and then 95°C for 5 minutes. After
subjects, and (3) to evaluate the relationship between fecal     incubation, one volume of isopropanol was mixed with the
microbiome and obesity, smoking status, and treatment con-       sample, passed through silica columns by centrifugation, and
dition of HS patients.                                           washed twice with washing buffer (20 mM NaCl, 2 mM Tris
                                                                 -HCl, pH 7.7, 80% v/v ethanol). DNA was eluted with 50
Materials and Methods                                            µL 100 mM Tris-HCl (pH) and stored at -20°C until an-
                                                                 alyzed. Spectrophotometric methods measured the amount
Study Population                                                 and quality of isolated DNA in samples, and their suitability
The study was conducted over the period from August 2018         to the next steps was tested. Next molecular processes were
to May 2019 at the Dermatology Department in Hacettepe           performed with DNA with OD260 / OD280 ratio of 1.8-2.0
University and enrolled 30 participants, including 15 pa-        and OD260 / OD230 ratio of 2.0-2 and at least 10 ng/ul
tients with HS and 15 age- and sex-matched healthy controls      (preferably 50-300 ng / µL) concentrations.
without HS and any other skin diseases. Patients with HS
and healthy subjects who were between the ages of 18-65          16S rRNA Amplification
years, without any systemic antibiotic therapy, probiotics, or   The amplification of the V3 and V4-conserved re-
prebiotics use in the last 3-months, who were not on a cur-      gions of bacterial 16S rRNA were performed by poly-
rent specific diet (vegan, vegetarian, gluten-free diet), who    merase chain reaction (PCR) using Illumina adapter
did not have concomitant systemic inflammatory disease,          overhang    nucleotide     16S     rRNA-specific      sequences,



2                                                                    Original Article | Dermatol Pract Concept. 2022;12(4):e2022191
5’-TCGTCGGCAGCGTCAGATGTGTATAAGAGA-                               One-sample t-test, Mann-Whitney U test, PERMANOVA,
CAG-CCTACGG GNGGCWGCAG-3’and 5’-GTCTCGT-                         and Kruskal-Wallis test were used for statistical significance
GGGCTCGGAGATGTGTATAAGAGACAGGACTACH-                              analysis. Statistical significance was set at P < 0.05.
VGGGTATCTAATCC-3’ for the forward and the reverse
primer, respectively. The first PCR was performed using the
Biospeedy® Proof Reading DNA Polymerase 2× Reaction
                                                                 Results
Mix (Bioeksen R&D Technologies) with 200 nm of each              The Characteristics of Participants
primer. Reactions were followed by exposure to 95°C for
                                                                 We enrolled 15 patients with HS and 15 age- and sex-matched
3 minutes, 25 cycles of 95°C for 30 seconds, 55°C for 30
                                                                 healthy controls in this study. All subjects were Turkish in
seconds, and 72°C for 30 seconds, and finally at 72°C for 5
                                                                 origin and coming from exact geographical locations. The
minutes. In order to verify the size (~550 bp), the products
                                                                 characteristics of study groups are shown in Table 1.
were moved on an agarose gel and purified using Biospeedy®
PCR Product Purification Kit (Bioeksen R&D Technologies).
                                                                 Fecal Microbiome Analysis Between HS
The dual indices and Illumina sequencing adapters were at-
                                                                 and Healthy Groups
tached to the purified PCR products via second PCR using
                                                                 Community Richness and Diversity
the Nextera XT Index Kit (Illumina Inc.) following the pro-
                                                                 The alpha-diversity of the gut microbiome was significantly
gram of 95°C for 3 minutes, 8 cycles at 95 °C for 30 seconds,
                                                                 lower in HS patients than healthy individuals (Shannon in-
55 °C for 30 seconds, 72 °C for 30 seconds and 72 °C for
                                                                 dex, P = 0.048). The Simpson, ACE, Chao, and Faith phy-
5 minutes. Finally, the products were purified again using
                                                                 lodiversity indices of HS patients were lower than those of
Biospeedy® PCR Product Purification Kit (Bioeksen R&D
                                                                 controls; however, the differences were not statistically sig-
Technologies). The size of the final library (~630 bp) was
                                                                 nificant (P > 0.05) (Figure 1).
verified by using Bioanalyzer DNA 1000 chip. The dilution
                                                                    The gut microbiome composition in HS patients was
of the final library to 4 nM was performed by adding 10 mM
                                                                 significantly distinct from healthy controls. The results of
Tris (pH 8.5), and the 5 μL aliquots were mixed for pool-
                                                                 Bray-Curtis and Jaccard Dissimilarity indices showed signifi-
ing libraries. Pooled libraries were denatured with NaOH to
                                                                 cantly different clustering of HS patients and healthy sub-
prepare for cluster generation and sequencing, diluted with
                                                                 jects based on PERMANOVA statistical analyses (P = 0.01
hybridization buffer (HT1) and denatured with heat before
                                                                 and P = 0.007, respectively), indicating that the bacterial
the MiSeq sequencing. The 16S rDNA gene amplification
                                                                 community structure in HS is different from that in healthy
products were sequenced on Illumina MiSeq Reagent Kit v3.
                                                                 controls (Figure 2).
Bioinformatics and Statistical Analyses
                                                                 Overall Taxonomic Analysis of HS Patients
The raw sequence data were processed using QIIME2                and Controls, Distribution at the Phylum Level
v2019.1 software. First, the barcode and the primers were        The gut microbiome of both HS patients and healthy controls was
trimmed, and unique sequences were identified. Pre-clustering    largely dominated by Firmicutes (relative abundance 92.64%
prevented redundancy. UCHIME was used for the removal            vs. 93.10%), Bacteroidetes (5.35% vs. 4.64%), ­Actinobacteria
of chimeras. Next, the sequences were classified using a clas-   (0.95% vs. 1.23%), unclassified Bacteria (0.4% vs. 0.54%),
sifier within QIIME2. The references and taxonomy files          Proteobacteria (0.52% vs. 0.4%) and Verrucomicrobia (0.52%
were obtained from the QIIME2 database. After picking op-        vs. 0.4%). The proportions of rare phyla including Synergys-
erational taxonomic units (OTU) at 97% sequence similarity       tetes, Tenericutes, Fusobacteria, Candidatus_Saccharibacteria,
and taxonomic assignments using the QIIME2 and SILVA             Acidobacteria, Chloroplast, and ­Cyanobacteria were present at
rDNA database, the OTUs were binned into phylotypes.             much lower levels. Firmicutes was the most predominant phy-
    Alpha diversity and beta diversity were calculated with      lum among all relatively abundant dominant taxa in HS and
QIIME2 v2019.1 software. The alpha diversity is defined as       healthy controls. The overall microbial composition of each
the diversity within a community and was calculated using        group at the phylum level is represented in Figure 3. The phy-
Shannon, Simpson’s, ACE, Chao, and Faith Phylogenetic di-        lum unclassified Bacteria was significantly reduced (P = 0.032)
versity indices. The beta diversity is defined as the distance   in the HS group compared to the healthy control, whereas other
between communities and was calculated by Bray-Curtis dis-       phyla showed no significant difference.
similarity and Jaccard distance and represented in a three-­
dimensional Principal Coordinate Axis on EMPeror. Statistical    Overall Taxonomic Analysis of HS Patients
analyses were performed using Statistical Package for Social     and Controls, Distribution at the Genus Level
Sciences version 20.0 (SPSS Inc., Chicago, IL, United States)    Lachnospiraceae_unclassified, Ruminococcaceae_unclas-
and MINITAB 17 software (Minitab Ltd. Co., Coventry, UK).        sified, Clostridiales_unclassified, Roseburia, Gemmiger,



Original Article | Dermatol Pract Concept. 2022;12(4):e2022191                                                                3
     Table 1. Characteristics of hidradenitis suppurativa patients (N = 15) and healthy individuals
                                     (N = 15) included in the study.
                   Characteristic                                  HS patients (N = 15)             Healthy controls (N = 15)               P
 Male / Female (N)                                                          10 / 5                              10 / 5
 Age, years, mean ± SD (range)                                     33.23 ± 12.29 (18-57)               33.23 ± 12.29 (18-57)
 BMI, mean ± SD                                                         28.63 ± 5.7                          24.7 ± 2.37                 0.026a
 Healthy weight (N)                                                         5                                    11
 Overweight (N)                                                             3                                     3
 Obese (N)                                                                  7                                     1
 Cigarette pack year, mean ± SD                                        13.13 ± 11.79                         4.93 ± 9.97                 0.011a
 Current smoker (N)                                                         13                                    4
 Non-smoker (N)                                                              2                                   11
 Disease onset, years, mean ± SD (range)                              24 ± 9.9 (15-48)                             -
 Family history (N)                                                         5 / 15                                 -
 Hurley stage (N)                                                                                                  -
 I                                                                            2
 II                                                                          10
 III                                                                          3
 Modified Sartorius Score                                               48.6 ± 33.6                                -
 IHS4 score, mean ± SD                                                 21.87 ± 15.25                               -
 Mild (N)                                                                    0
 Moderate (N)                                                                4
 Severe (N)                                                                 11
 Visual Analoge Scale, mean ± SD (range)                             7.53 ± 1.76 (5-10)                            -
 Medication use (N)                                                         5 / 10                                 -
 Systemic retinoids                                                           4
 Adalimumab                                                                   1

BMI = body mass index; HS = hidradenitis suppurativa; IHS4 = International hidradenitis suppurativa severity score system; SD = standard
deviation, a P < 0.05.




                                             7,6

                                             7,4

                                             7,2

                                             7,0
                   SHANNON DIVERSITY INDEX




                                             6,8

                                             6,6

                                             6,4

                                             6,2

                                             6,0

                                             5,8

                                             5,6

                                             5,4
                                                   HEALTHY CONTROL (n=15)            HIDRADENITIS SUPPURATIVA (n=15)

                 Figure 1. Alpha diversity of the gut microbiome of HS patients and healthy subjects. Shannon index box
                 and whiskers plots showed significantly reduced alpha diversity in HS patients (P = 0.048). HS = hidra-
                 denitis suppurativa.



4                                                                                    Original Article | Dermatol Pract Concept. 2022;12(4):e2022191
                  Axis 2 (7.931 %)




                                                                                                               Axis 1 (9.696 %)



                                                                                                                HS (n=15)
                                                                                                                Healthy (n=15)
                     Axis 3 (7.519 %)

              Figure 2. Beta diversity of the gut microbiome of HS patients and healthy subjects. Each data point represents
              an individual sample. Jaccard Dissimilarity Index showed significantly different microbiome clustering of HS
              patients and healthy subjects (P = 0.007) presented through principal coordinate Axis 1, indicating that the
              bacterial community structure in HS is different from that in healthy controls. HS = hidradenitis suppurativa.



              100%
                       92.64% 93.10%
               90%


               80%


               70%


               60%


               50%


               40%


               30%


               20%


               10%                      5.35% 4.64%
                                                           0.95% 1.23%       0.52%0.40%          0.40% 0.54%        0.52% 0.40%
                0%
                                             es
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                                                            HS (n=15)    Control (n=15)


             Figure 3. Relative abundance of the gut microbiome distribution at the phylum level. The phylum Bacteria_un-
             classified was significantly reduced (P= 0.032) in the HS group compared to the healthy controls, whereas other
             phyla showed no significant difference. * P < 0.05 HS = hidradenitis suppurativa.



Original Article | Dermatol Pract Concept. 2022;12(4):e2022191                                                                    5
Coprococcus, Blautia, Ruminococcus2, Fusicatenibacter,                         genus level showed no significant taxa alterations among
Faecalibacterium, Dorea, Firmicutes_unclassified, Dial-                        non-obese and obese, non-smokers and smokers, and treat-
ister, and Ruminococcus were main genera (>1%) in both                         ment naïve and under treatment groups.
groups. In HS and control groups, Lachnospiraceae_unclas-
sified (28.85% vs. 27.35%), Ruminococcaceae_unclassified
                                                                               Conclusions
(10.68% vs. 11.54%), Clostridiales_unclassified (7.90% vs.
9.07%), and Roseburia (9.96% vs. 8.66%) were the four                          Based on our hypothesis that the gut microbiome of patients
commonest genera. Among all genera, the relative abun-                         with HS is different from healthy people, we conducted a
dance of Clostridiales_unclassified, Firmicutes_unclassified,                  16S rRNA-based metagenomics analysis of fecal samples in
and Fusicatenibacter in HS was significantly lower than in                     patients with HS and demonstrated a dysbiotic state in HS
controls (P= 0.005, P= 0.029, and P= 0.046, respectively)                      patients. We showed significantly decreased alpha diversity of
(Figure 4).                                                                    gut microbiome in patients with HS, indicating lower bacterial
                                                                               community richness than healthy controls. In addition, bacte-
Analysis of Fecal Microbiome When Stratified                                   rial community structure, beta diversity, was significantly dif-
by BMI, Smoking Status, and Treatment                                          ferent between patients with HS and healthy controls.
of HS Patients                                                                    Previous studies on gut microbiome alterations in HS
Shannon and Simpson diversity indices showed no signifi-                       patients are summarized in Table 2 [11-14]. Kam et al and
cant differences between non-obese and obese, non-smokers                      McCarthy et al showed decreased alpha diversity in HS pa-
and smokers, and treatment naïve and under treatment                           tients in line with our results [12,14]. However, the bacte-
groups analyzing alpha-diversity (P= 0.536 and P= 0.281,                       rial community structure of HS patients was different from
P=0.076 and P=0.076, P=0.440 and P=0.254, respectively).                       that of healthy people only in McCarthy et al study [14].
Fecal microbiome composition evaluated by Bray-Curtis and                      When we compared the bacteria distribution at the phylum
Jaccard Dissimilarity indices was not significantly different                  level, there was no significant difference other than unclas-
among non-obese and obese, non-smokers and smokers,                            sified bacteria phylum between HS and healthy subjects in
and treatment naïve and under treatment groups (P=0.656                        our study. On the other hand, our results indicated that the
and P=0.73, P=0.883 and P=0.729, P=0.391 and P=0.648,                          abundance of three genera had been significantly reduced in
respectively). Taxonomic analysis at the phylum and the                        HS patients: unclassified Clostridiales, Fusicatenibacter, and




                 Ruminococcus      1.44%
                                   1.31%
                      Dialister     1.43%
                                   1.28%
      Firmicutes_unclassified*                                9.07%
                                                          7.90%
                         Dorea     1.62%
                                   1.54%
              Faecalibacterium                    5.35%
                                                 5.15%
              Fusicatenibacter*         3.00%
                                      2.51%
               Ruminococcus2          2.42%
                                       2.78%
                        Blautia       2.31%
                                      2.49%
                  Coprococcus                   5.39%
                                              4.81%
                    Gemmiger                    4.98%
                                                4.90%
                     Roseburia                              8.66%
                                                                9.96%
    Clostridiales_unclassified*                               9.07%
                                                          7.90%
Ruminococcaceae_unclassified                                          11.54%
                                                                   10.68%
                                                                                                                         27.35%
 Lachnospiraceae_unclassified
                                                                                                                             28.85%
                              0%            5%               10%                15%             20%            25%            30%            35%

                                                               Control (n=15)    HS (n=15)


Figure 4. Relative abundance of the gut microbiome distribution at the genus level. The relative abundance of three genera: unclassified
Clostridiales, unclassified Firmicutes, and Fusicatenibacter in HS was significantly lower than that in controls (P = 0.005, P = 0.029, and
P = 0.046, respectively). * P < 0.05 HS = hidradenitis suppurativa.


6                                                                                     Original Article | Dermatol Pract Concept. 2022;12(4):e2022191
                           Table 2. Gut microbiome studies conducted with HS patient.
                                                                The minimum
                                                                time interval                                           Main findings on the
                                                                   between                                              relative abundances
                                           Current    Method      antibiotic                                               of gut bacteria
                                         treatment   of the gut   usage and                                               in HS patients in
              Study                       status of  microbiome     sample              Alpha-            Beta-            comparison to
           participants    Ethnicity    participants  analysis    collection           diversity        diversity         healthy controls
Present    15 HS vs. 15 All             4 patients on Fecal           3 months        Decreased        Signifi-        Decreased relative
study      HC           Caucasians      systemic ret- samples                         alpha-diver-     cantly          abundance of phylum
                                        inoid and     16S rRNA                        sity in Shan-    different       Unclassified_bacteria
                                        1 patient on                                  non index        bacterial       Decreased relative
                                        anti-TNF-α                                    No signifi-      compo-          abundance of 3
                                        therapy                                       cant results     sitions in      genera: Clostridia-
                                                                                      in Simpson,      Bray-Cur-       les_unclassified, Firmic-
                                                                                      Faith’s          tis and         utes_unclassified, and
                                                                                      phylodiver-      Jaccard         Fusicatenibacter
                                                                                      sity, ACE,       Dissimilar-
                                                                                      and Chao         ity Indices
                                                                                      indices
Eppinga 17 HS vs. 33 76% of HS          1 patient on   Fecal          8 weeks                      -                 - No difference in the
et al,  HC           and HC are         anti-TNF-α     samples                                                         relative abundance of
2016                 Caucasians         therapy        Quantitative                                                    Faecalibacterium praus-
[11]                                                   PCR                                                             nitzii or Escherichia coli
Kam        3 HS vs. 3     African-      Not            Fecal          4 weeks         Decreased        No sig-         Decreased relative
et al,     HC             American:     specified      samples                        alpha-diver-     nificant        abundance of phylum
2021                      3 and                        16S rRNA                       sity in Shan-    differences     Firmicutes
[12]2                     Hispanic: 0                                                 non index        in UniFrac      Increased relative abun-
                          in HS group                                                 No sig-          distance        dance of Bilophila and
                          African-                                                    nificant         matrices        Holdemania
                          American:                                                   results in                       Decreased relative
                          2 and                                                       the number                       abundance of Lach-
                          Hispanic: 1                                                 of observed                      nobacterium and
                          in the HC                                                   OTUs                             Veillonella
                          group
Lam et 17 HS vs. 20 13 Cauca-           1 patient on   Fecal          8 weeks and 7   No signifi-      No signif-      Increased relative abun-
al, 2021 HC         sians in the        anti-TNF-α     samples        days            cant results     icant dif-      dance of Robinsoniella,
[13[]               HS group            therapy        16S rRNA                       in bacterial     ferences in     Sellimonas, Eggerthella,
                    and 15              9 patients                                    richness,        Bray-Cur-       Flavonifractor, Oscilli-
                    Caucasians          on topical                                    Shannon          tis and         bacter, Lachnıclostrid-
                    in the HC           therapy                                       and, inverse     Jaccard         ium, and Romboutsia
                    group                                                             Simpson          Dissimilar-     Decreased rela-
                                                                                      Indices          ity Indices     tive abundance of
                                                                                                                       Parasporobacterium
                                                                                                                       Decreased rela-
                                                                                                                       tive abundance of
                                                                                                                       Christensenellaceae,
                                                                                                                       Lachnospiraceae, and
                                                                                                                       Porphyromonaceae

HC = healthy controls; HS = hidradenitis suppurativa; out = operational taxonomic unit; rRNA = ribosomal ribonucleic acid; TNF = tumor
necrosis factor.



unclassified Firmicutes. Various taxa alterations have been            without concomitant inflammatory bowel diseases (IBD):
noted in studies conducted with HS patients, and there was             Faecalibacterium prausnitzii and Escherichia coli. The study
no common bacterial taxa alteration between our study and              reported significantly reduced Faecalibacterium prausnitzii
the other study results (Table 2) [11-14]. These differences           in solely psoriasis patients, psoriasis with IBD patients, and
between study results in taxa distribution could be attributed         IBD patients. In addition, the study showed a significant re-
to ethnic diversity and consequently different dietary habits          duction in the abundance of Faecalibacterium prausnitzii in
of the study samples [17].                                             patients with concomitant IBD and HS. However, there was
    Eppinga et al investigated the abundance of two species            no significant difference in Faecalibacterium prausnitzii in
in the gut microbiome of psoriasis and HS patients with and            patients with solely HS.11 Compatibly, the abundance of the


Original Article | Dermatol Pract Concept. 2022;12(4):e2022191                                                                                 7
genus Faecalibacterium was not different between HS and           literature show the effect of smoking on the gut microbiome.
healthy subjects in our study.                                    These studies have found an association between smoking
    The gut microbiome plays a critical role in human health      status and gut microbiome composition, which is that the
through the development of immune responses mediated by           composition of the gut microbiome of smokers is different
metabolic products and inflammatory signaling pathways            from that of non-smokers [33-35]. In our study, there were
[18]. It has been shown that commensal bacteria produce           no significant differences neither in diversity nor taxa dis-
immunomodulatory metabolites, particularly short-chain            tribution between the gut microbiome of obese and healthy
fatty acids (SCFAs) like butyrate, propionate, and acetate.       subjects or the gut microbiome of smokers and non-smokers.
These metabolites have anti-inflammatory actions mediated            Several limitations of this study should be noted. First,
by G-protein coupled receptors and contribute to the epithe-      we could not perform a power analysis, and the sample size
lial barrier integrity [19]. Short-chain fatty acids producing    was small in study subgroups. Larger sample size should be
bacteria induce peripheral T-regulatory cells (Tregs), elimi-     concluded with more significant results in future studies.
nate the Th17/Th1 response and provide a balance between          Second, although we excluded participants using antibiotics,
pro-inflammatory and anti-inflammatory immune cells               probiotics, prebiotics, and on a specific diet, not following
[6,20-23]. Some bacterial taxa are well-characterized with        a standard diet among participants may have affected the
their anti-inflammatory properties. For example, Firmic-          composition of the gut microbiome. Third, there were five
utes phylum is known for its anti-inflammatory actions via        HS patients under treatment during fecal sample collection
producing SCFAs [18]. Three genera, unclassified Clostridi-       in our study. We did not find significant differences in di-
ales, Fusicatenibacter, and unclassified Firmicutes that were     versity and bacteria distribution between patients under and
shown to be decreased in our study, belong to Firmicutes          without treatment. Nevertheless, the inclusion of patients
phylum. Faecalibacterium prausnitzii and Roseburia species        with similar treatment status is warranted to understand
are other well-known anti-inflammatory bacteria and play a        better the gut microbiome's role in the pathogenesis of HS.
critical role in IBD [24,25]. The relative abundance of Fae-         This study indicated that significant alterations in the
calibacterium and Roseburia was not different between the         gut microbiome of HS patients could play a critical role in
gut microbiome of patients with HS and healthy controls.          the pathogenesis of HS. These findings also provide further
However, decreased abundance of Fusicatenibacter was re-          insights that the gut–skin axis contributes to the pathogen-
markable in HS patients. Fusicatenibacter saccharivorans is a     esis of chronic inflammatory skin disorders. Further inves-
recently isolated and cultured bacterium and a strain of Clos-    tigations are required to explain the connections between
tridium subcluster XIVa that induces Tregs and produces bu-       the gut microbiome and the pathogenesis of HS. Increased
tyrate and other SCFAs [26,27]. A recent study has reported       understanding of the pathogenesis of HS will shed light on
that F .saccharivorans decreased in patients with active ulcer-   the new potential therapeutic targets, and novel treatment
ative colitis (UC), and there is a negative correlation between   options such as probiotic and prebiotic supplementation or
the abundance of Fusicatenibacter saccharivorans and UC           even fecal microbiome transplantation will arise in the man-
activity [28]. Therefore, a lower abundance of unclassified       agement of this challenging chronic skin disorder.
Clostridiales, Fusicatenibacter, and unclassified Firmicutes in
the gut microbiome of patients with HS may be a triggering
factor for systemic inflammation through decreased SCFA           References
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