Hidradenitis suppurativa (HS)/acne inversa is a debilitating chronic disease that remains poorly understood and difficult to manage. Clinical practice is variable, and there is a need for international, evidence-based and easily applicable consensus on HS management. We report here the findings of a systematic literature review, which were subsequently used as a basis for the development of international consensus recommendations for the management of patients with HS. A systematic literature review was performed for each of nine clinical questions in HS (defined by an expert steering committee), covering comorbidity assessment, therapy (medical, surgical and combinations) and response to treatment. Included articles underwent data extraction and were graded according to the Oxford Centre for Evidence-based Medicine criteria. Evidence-based recommendations were then drafted, refined and voted upon, using a modified Delphi process. Overall, 5310 articles were screened, 171 articles were analysed, and 65 were used to derive recommendations. These articles included six randomized controlled trials plus cohort studies and case series. The highest level of evidence concerned dosing recommendations for topical clindamycin in mild disease (with systemic tetracyclines for more frequent/widespread lesions) and biologic therapy (especially adalimumab) as second-line agents (following conventional therapy failure). Good-quality evidence was available for the hidradenitis suppurativa clinical response (HiSCR) as a dichotomous outcome measure in inflammatory areas under treatment. Lower-level evidence supported recommendations for topical triclosan and oral zinc in mild-to-moderate HS, systemic clindamycin and rifampicin in moderate HS and intravenous ertapenem in selected patients with more severe disease. Intralesional or systemic steroids may also be considered. Local surgical excision is suggested for mild-to-moderate HS, with wide excision for more extensive disease. Despite a paucity of good-quality data on management decisions in HS, this systematic review has enabled the development of robust and easily applicable clinical recommendations for international physicians based on graded evidence.

IMPORTANCE Although the pathogenesis of hidradenitis suppurativa (HS) remains enigmatic, several factors point to potential involvement of the cutaneous microbiome. Insight into the cutaneous microbiome in HS using next-generation sequencing may provide novel data on the microbiological diversity of the skin. OBJECTIVE To investigate the follicular skin microbiome in patients with HS and in healthy controls.

Hidradenitis suppurativa (HS) is a chronic inflammatory disabling skin disease consisting of recurrent nodules, sinuses, fistulas and scarring involving the intertriginous regions. HS is often a therapeutic challenge and most treatments are off-label. A better understanding of aetiology and pathogenesis of HS may facilitate the development of effective treatment. Although the clinical presentation is strongly reminiscent of bacterial infection, the role of bacteria remains controversial. Studies have isolated an array of different bacteria specimens. Consistent findings of Gram-positive cocci and Gram-positive rods including Staphylococus aureus, coagulase-negative staphylococci (CoNS) and Corynebacterium species in deep tissue samples have been demonstrated in HS and may constitute a central target for the immune system. Efficacy of antibiotics, that is rifampicin, clindamycin or tetracycline, supports a microbial role in disease pathogenesis. However, these antibiotics also work as immunomodulators of especially T cells, and the underlying mechanisms may therefore be more complex. We performed a systematic review of previous studies investigating the bacterial flora in hidradenitis suppurativa. We searched PubMed, EMBASE, Royal Danish Library and Cochrane library (search date 11 December 2014). A total of 66 papers were identified and nine papers published between 1988 and 2014 matched our inclusion criteria, yielding bacteriological data of a total of 324 patients with HS (mean age 36.8 years and female/male ratio 215/109). This overview of the bacteriology may aid researchers and physicians exploring the potential role of bacteria in HS. Furthermore, to stimulate a broader debate, we also present different viewpoints on the possible role of bacteria in HS.