Laboratory Studies
Several studies may be requested, depending on the clinical presentation.
Gram stain may be performed on a skin scraping, which may show gram-positive rods; however, the stain often is negative because the infection is deep, and the microorganism is not reached with scraping.
Bacterial culture on special media fortified with serum and at room temperature may be attempted. Culture of a biopsy from the leading edge of the lesion may reveal the organism.
Blood culture aids in the diagnosis of systemic erysipeloid. [17]
Skin biopsy may be taken to confirm the diagnosis (see Histologic Findings).
Organism culture is difficult. Media requires enrichment with blood and incubation with 5-10% carbon dioxide. [19]
Imaging Studies
Imaging studies usually are ordered when an individual has the systemic form of erysipeloid, depending on the clinical presentation and probability of organ involvement.
Echocardiography may be ordered if endocarditis is suspected.
Computed tomography or magnetic resonance imaging of the brain may be used to rule out brain abscess or cerebral infarct.
Radiography or CT of the chest may be ordered if pleural effusion is suspected.
Bone scan or MRI of bone may be performed if osseous necrosis is suspected.
Histologic Findings
Histopathologic examination is nonspecific. Papillary edema and vascular dilatation and dermal neutrophilic and lymphocytic infiltrate are observed. The epidermis shows spongiosis, which may be severe enough to cause intraepidermal vesiculation. Marked edema of the papillary dermis with dilatation of blood and lymphatic vessels occurs. In the reticular dermis, a perivascular inflammatory cell infiltrate made of neutrophils and eosinophils is observed.
-
Erysipeloid. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/topics/erysipeloid/) and the Waikato District Health Board (http://www.waikatodhb.health.nz/).
-
Erysipeloid. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/topics/erysipeloid/) and the Waikato District Health Board (http://www.waikatodhb.health.nz/).
