One of the mainstays of therapy for mild hidradenitis suppurativa is antibiotic therapy. The etiology of hidradenitis suppurativa has long been debated. The most widely accepted theory posits that keratin plugging of the hair follicle leads to follicular dilation, rupture, and surrounding inflammation. What part bacteria play in the process is still under debate. Does bacterial invasion trigger inflammatory pathways? Or is bacterial invasion secondary? The fact that clindamycin, rifampicin, and tetracycline, which are three of the most effective antibiotics used in hidradenitis suppurativa, have known anti-inflammatory properties also clouds the issue. Ring et al. published a review of 9 studies from between 1988 and 2014 on the bacteriology of hidradenitis suppurativa. Most of these bacteriologic studies did not confine themselves to one area, i.e., they contained patients suffering from axillary hidradenitis, inguinal lesions, vulvar and scrotal lesions, as well as perianal disease, or a combination of these. They also did not break down the microbiologic findings by site of collection [47]. A 1988 study by Highet et al., confined itself to microbiology of perineal hidradenitis suppurativa. This included perianal, upper thigh, inguinal, buttock, and genital lesions. The authors implicated Streptococcus milleri most significantly in causing disease exacerbation in their patients, and antibiotics clearing that bacterium were often successful in improving suppuration. Staphylococcus aureus was implicated as well, but to a lesser degree. Interestingly, coagulase negative staphylococcus (CoNS) was frequently cultured from patients, but was essentially disregarded as being a ubiquitous commensal and considered nonpathogenic [48]. Subsequent studies have lent CoNS much more of a role in propagation of the disease process because of its production of a biofilm (“slime”), a matrix of extracellular polymeric substance comprised of proteins, polysaccharides, and extracellular DNA. The bacteria which produce this biofilm are embedded in the slime, which gives them some protection from antibiotics as well as natural host defenses. Both Staphylococcus epidermidis and Staphylococcus lugdunensis are coagulase negative staph species that produce biofilm. Both have been implicated in hidradenitis suppurativa lesions [49–51].

Anaerobic actinomycetes (Actinomyces turicensis, Actinomyces radingae, Actinomyces neuii, and Actinobaculum schaalii) have been recovered from a majority of hidradenitis suppurativa lesions in later studies. These species are slow growing and difficult to identify, which may account for them not being cultured in earlier studies. They typically are difficult to eradicate and require prolonged antibiosis. They usually coexist with strict anaerobes [50, 52].

Finally, there exists a case report of a patient with gluteal hidradenitis suppurativa who underwent ileostomy and local incisions and drainages, fistulectomies, and unroofings, only to have his sepsis recur on ileostomy reversal. A large resection of one buttock was performed, with a finding of a 9 mm larva of Ancyclostoma braziliense (hookworm) in one of the abscess cavities. This larva is responsible for cutaneous larva migrans when it migrates through the skin causing serpiginous raised tunnels. In this case, it was felt that the larva may have incited further inflammation. It was not implicated as causing the hidradenitis suppurativa [53].

In summary, many bacterial species have been implicated in pathogenesis or superinfection of hidradenitis lesions, including skin commensals, such as coagulase negative staph species S epidermidis and lugdunensis, Streptococcus milleri, pathogens, such as Staph aureus and actinomycetes, as well as rarer bacteria such as Bilophila wadsworthia that colonize the GI tract, but have been implicated in other disease processes such as appendicitis [54]. Antibiotic regimens active against these may result in improvement in suppurative lesions, but recurrence after their cessation is the norm. In addition, many of the more common antibiotic regimens used in hidradenitis suppurativa employ clindamycin, tetracycline, and rifampin, that have anti-inflammatory properties which may account for some of their beneficial effects in hidradenitis.

Perianal and gluteal hidradenitis suppurativa is a chronic, relapsing disease capable of causing patients great disability and decreased quality of life. There is still often a significant delay in diagnosis. While a myriad of medical treatments can afford temporary relief, surgical excision is the most effective means of cure. Prolonged disease can be associated with the development of squamous cell carcinoma. These neoplasms tend to be more aggressive than denovo squamous cell carcinoma. Early diagnosis and appropriate R0 resection, if possible, is the only means of cure. Patients with long-standing hidradenitis in the perianal and gluteal areas need to be adequately informed of the risk of development of cancer.