• Dermatology
• Diagnostic
• Hidradenitis suppurativa
• Inflammation
• Moleculight
• pH wound healing

Introduction & Objectives:
Hidradenitis suppurativa (HS) is an inflammatory skin disease characterized by painful nodule, abscesses and tunnel, whose aetiology is still poorly understood. In recent years, researchers investigated the potential role of bacteria in HS, but conflicting results have emerged. It still remains uncertain whether bacteria play a role in HS pathogenesis or, more likely, may represent a consequence of the ongoing inflammatory process. The aim of the study is to correlate clinical and non-invasive diagnostic methods (pH and fluorescence) with microbiological examination in patients affected by moderate to severe HS. The primary endpoint of the study is to find a correlation between the pH of an actively draining lesion and the clinical inflammatory status. The secondary endpoint of the study is to correlate the bacterial load present with the fluorescence observed using MolecuLight i:X device.

Materials & Methods:
A group of 17 patients (5 males and 12 females) with moderate and severe HS localized to the axilla (7/17), groin (8/17) and gluteal region (2/17) were enrolled. All the patients presented HS tunnels in the absence of clinical signs of infection or critical colonization. Microbiological analysis was performed prior to antibiotic treatment: superficial cutaneous swab samples and punch biopsy samples of HS lesions were collected and the aerobic microflora cultured and quantitatively measured from each sample under standard laboratory conditions. Moreover, pH measurements were performed at the level of draining tunnels and the perilesional skin areas and a non-invasive auto-endogenous fluorescence device was used to detect bacterial loads in HS lesional and perilesional skin.

Results:
Microbiological culture analyses demonstrated that almost all samples were polymicrobial
containing at least 2 or 3 different bacterial species. Bacterial load of swab samples (CFU/gr) was
significantly higher than biopsy samples (P<0.05). Most of the bacteria isolated were part of the
normal microbial flora of the skin. Among them, Staphylococcus spp was isolated at higher frequency (from 12/17 biopsies and from all the swab samples) followed by Corynebacterium spp (from 7/17 biopsies and from 10/17 swabs). Proteus mirabilis, a component not usually part of the skin microflora was isolated from 3 biopsy samples, but from only one swab sample.
The non-invasive auto-endogenous fluorescence device showed increased red coloration in patients who had skin swabs positive for Staphylococcus spp. 12/17 patients showed pH measurements within the normal range (6.5 - 7.5) for both lesional and perilesional skin, while in the 5/17 patients, that revealed pH values ranging from 7.5 to 8.8, clinical signs of active inflammation (drainage, intense pain and oedema) were observed.
We found a statistically significant correlation between wound pH and clinical inflammatory response. Finally, we found a statistically significant correlation between red fluorescence detected at the wound site using the Moleculight i:X device and bacterial colonization by Staphylococcus spp.

Conclusion:
Our preliminary results revealed a dominant colonization of HS lesion with normal skin commensal flora, detected either by microbiological examination and through the fluorescence device. This observation suggests that commensal bacteria may elicit inflammatory responses in genetically susceptible individuals. Microbiome analysis of profound HS lesions (biopsy samples) compared to the superficial (swab) ones may give further insights to the role of bacteria in the etio-pathogenesis of the disease.
Furthermore, the finding of higher pH values in patients with actively draining but clinically and microbiologically non-infected lesions might suggest that this biochemical parameter could serve as a biomarker indicative of a pro-inflammatory microenvironment. Further investigations with larger samples are necessary to understand the complex integration between pH values and the inflammatory or infectious status of HS lesions.