Bacteria Found in HS Lesions

Although the HS etiology is unknown, a large variety of microorganisms can be isolated from the lesions. The clinical picture of the disease resembles an infectious process and various

Table 11.2. Studies describing the diversity of bacteria found in various HS lesions

Table 11.2. Studies describing the diversity of bacteria found in various HS lesions

Investigator

Bacteria found

Area of the skin

Leach et al. [S5]

Staphylococcus aureus, anaerobic bacteria

Axillae

Brenner and Lookingbill [7]

Staphylococcus aureus, Staphylococcus epidermidis Bacteroides fragilis, Bacteroides melaninogenicus

Perirectal, groin, axillae

Highet et al. [2S]

Streptococcus milleri

Perineal

Highet et al. [24]

Streptococcus milleri, Staphylococcus aureus, anaerobic streptococci, Bacteroides species

Perineal

Finegold et al. [18]

Biophila wadsworthia

Axillae

Bendahan et al. [5]

Chlamydia trachomatis

Perineal

Jemec et al. [29]

Staphylococcus aureus, Streptococcus milleri, Staphylococcus epidermidis, Staphylococcus hominis

Axillae, groin, breasts, buttocks

Brook and Frazier [S]

Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa; Peptostreptococcus species, Prevotella species, micro-aerophilic streptococci, Fusobacterium species, Bacteroides species

Axillae

Lapins et al. [SS]

Staphylococcus aureus, coagulase-negative staphylococci, enterococci, group B hemolytic streptococci, group C hemolytic streptococci, Bacillus cereus, diphtheroides, enterobacteriacae-; Peptostreptococcus species, Propionibacterium acnes, microaerophilic streptococci, Lactobacillus species, Bacteroides fragilis, other Bacteroides species, Prevotella species

Axillae and perineal

bacteria are suspected as being responsible for the inflammation. The bacterial findings are considered by some authors as either contaminants from the normal skin flora or a result of secondary infection in a previously sterile process [33].

Despite the volume of the discharge the HS lesions are often found to be sterile [29, 33], but sometimes a large variety of microorganisms can be isolated from the sinuses, particularly staphylococci, streptococci, Gram-negative rods, and anaerobic bacteria (Table 11.2). The bacterial flora are not consistent and may change unpredictably [31]. Brook and Frazier [8] found, in a retrospective review of clinical and bacteriological data from patients with axillary disease, that the most prevalent aerobic bacteria were Staphylococcus aureus, Streptococcus pyogenes, and Pseudomonas aeruginosa and the most frequent anaerobic bacteria were Peptostreptococ-cus species, Prevotella species, microaerophilic streptococci, Fusobacterium species, and Bacte-roides species.

In most of the studies samples are collected from the surface of the lesions [22-24] and there is a high risk of contamination with the resident skin flora. In these conditions the bacteriological results are difficult to interpret. Jemec et al. [29] have aspirated pus from the deeper parts of HS. Bacteria were found in half of active lesions: Staphylococcus aureus and coagulase-negative staphylococci (Staphylococcus epidermidis and Staphylococcus hominis) were most commonly isolated. An explanation for the large number of negative cultures could be that it is difficult to localize the infected part using the aspiration technique. It was found that the duration of the disease was shorter for those patients in whom Staphylococcus aureus was detected as a possible etiological factor, indicating that this bacterium may be involved early in the disease pathogene-sis by causing anatomical changes in the hair

Bacteriology of Hidradenitis Suppurativa

Table 11.3. Possible factors responsible for coagulase-negative staphylococci pathogenicity in HS lesions

Factors

Effect

Sinus formation in HS lesions

Enhances the pathogenic properties of the bacteria [33]

Bacterial capacity of biofilm formation

Protects against antibiotics and from attacks by the immune system [42]

Bacterial production of lipases, proteases, and other exoenzymes

Persistence in the host. Tissue degradation [42]

Toxin production

Invasion properties [35, 36]

Production of PASpositive extracellular polysaccharide substance

Obstructs the delivery of sweat to the skin surface [37]

follicles. These modifications may later predispose to inflammation independently of the presence of bacteria [29].

Lapins et al. [33] circumvented problems both of contamination and of missing the active area of infection by using a carbon dioxide (CO2) laser surgical method to evaporate the diseased tissue level by level from the surface downwards. This allows sampling for bacteriological cultures from each level without the risk of contamination with bacteria from the level above. By using this method, bacteria were found even in the deeper and closed parts of HS. Staphylococcus aureus and coagulase-negative staphylococci were also the most commonly found species. After the Staphylococcus species the most commonly cultured bacteria were the anaerobic species found in the deeper levels: Peptostreptococcus species and Propionibacteri-um acnes. The aerobic bacteria were found in 60% of positive cultures at deep levels.

The clinical significance of coagulase-nega-tive staphylococci is unclear because while they are part of the normal microflora [29, 33] they have also gained attention as pathogens (Table 11.3). Coagulase-negative staphylococci are associated with infections in those with intravas-cular catheters [46] and prosthetic devices [14] where the presence of the foreign body will in crease the pathogenic properties of these otherwise harmless members of the normal flora. Lapins et al. [33] have often found coagulase-negative staphylococci as the sole bacteria in the deep portion of the lesions and suggested that the abnormally structural tissue in HS due to sinus formation can provide a medium similar to the presence of a foreign body and the result will be enhancement of the pathogenic properties of coagulase-negative staphylococci. Generally, the pathogenic potential of coagulase-nega-tive staphylococci is mainly due to their capacity to form biofilms on medical devices [42]. The sinus formation in HS may be an ideal place for biofilm formation and this microbiologic principle may be applicable to coagulase-negative staphylococci in HS. Many coagulase-negative staphylococci produce several lipases, proteases, and other exoenzymes, which possibly contribute to the persistence of coagulase-negative staphylococci in the host and may degrade host tissue [42]. Here, the bacteria find protection against antibiotics and from attacks by the immune system. The biofilm model was recently proposed to be involved in acne pathogenesis, where glycocalyx polymer secreted by Propioni-bacterium acnes as a biofilm may explain the immunogenicity of the organism as well as the unpredictable course of the disease [11]. There are also some lines of evidence that under certain conditions they may produce similar toxins to Staphylococcus aureus and could cause invasive diseases [36, 56].

Mowad et al. [37] showed that periodic-acid-Schiff- (PAS-) positive extracellular polysaccha-ride substance produced by Staphylococcus epi-dermidis obstructs the delivery of sweat to the skin surface and these strains are involved in the pathogenesis of miliaria. It was speculated that a similar mechanism could be involved in HS pathogenesis [33]. It is known that the pathogenic potential of coagulase-negative staphylococci varies according to species [33]. Staphylococcus haemolyticus and Staphylococ-cus saprophyticus have well-known pathogenic potential and Staphylococcus lugdunesis, Staphylococcus schleiferi or Staphylococcus caprae are considered emerging pathogens [56]. Staphylo-coccus lugdunesis was found in axillary lesions diagnosed as HS [54].

Streptococcus milleri, a microaerophilic microorganism frequently causing pyogenic infections [17] that often colonizes the gastrointestinal tract and female genital tract, was found by some investigators to be a major pathogen in perineal HS. Furthermore, the presence of this bacterium correlated with the disease activity and its elimination by appropriate antibiotic therapy was accompanied by marked clinical improvements [23, 24]. Microaerophilic streptococci were found by Brunsting in 1939 in a group of patients with HS [9]. Streptococcus mil-leri, Staphylococcus aureus, anaerobic streptococci, or Bacteroides species were frequently isolated in a group of 32 patients with active perineal HS [24]. Other authors could not find Streptococcus milleri in any of the specimens [41].

In perianal forms of HS, Escherichia coli, Klebsiella and Proteus strains as well as anaerobic bacteria were isolated [27]. Brenner and Lookingbill [7] have recovered Bacteroides species from perirectal, groin and axillae and the patients responded well to a suitable antibiotic treatment regimen. They suggest that the presence of anaerobic bacteria may reflect the chro-nicity of pre-existing local infection. Anaerobic bacteria were also isolated by Leach et al. from recurrent axillary lesions of HS [35].

Bilophila wadsworthia is a Gram-negative anaerobic rod found as part of the normal flora in feces and, occasionally, in saliva and in the vagina; in one case of HS it was isolated together with other anaerobic bacteria of the Prevotella species [4, 18].

Bendahan et al. [5] found an association between perineal HS lesions and Chlamydia trachomatis infection, but it was not clear whether the latter was a direct cause or a predisposing factor. These findings have not been confirmed by other authors.

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