Erysipeloid is a cutaneous infection caused by a bacterial pathogen Erysipelothrix rhusiopathiae. Skin injury and subsequent occupational exposure to livestock and other animals result in a cellulitis-like lesion, but several distinguishing characteristics may be identified. Patient history, clinical signs and microbiological investigations are necessary during workup, but the diagnosis can be made based on clinical criteria.
Erysipeloid is considered to be a zoonotic infection, meaning that exposure to contaminated animal products is a mandatory step in the pathogenesis of the infection  . Chicken, turkey, and fish are common animal hosts of Erysipelothrix rhusiopathiae, and its transfer to humans almost exclusively happens after fishing, livestock handling or other occupations involving animal contact   . The organism is inoculated onto previously abraded or injured skin (as a result of occupational or accidental injury), and after an incubation period of several days (2-7 in most cases), initial signs and symptoms appear. Because of the nature of acquisition of the infection, lesions predominantly appear on the hands and fingers  . Some patients may experience an asymptomatic course of the disease, but burning, itching or throbbing pain at the site of skin injury followed by edema, erythema, and localized inflammation is a typical finding  . The lesion is well-defined, contains raised edges and mimics subacute cellulitis, which is why it is often misdiagnosed as erysipelas or cellulitis, caused by streptococcal or staphylococcal species, respectively  . Furthermore, the absence of suppuration, together with a history of animal contact and immense pain, are distinguishing features of erysipeloid . In addition, vesicles, bullae, and erosions can be encountered, while proximal lymphadenopathy and signs of more severe infection (fever, arthralgia) are seen in a small number of cases  . In the majority of cases, the clinical course is self-limiting, and spontaneous resolution is seen within 3-4 weeks without the need for antibiotic therapy, but in rare cases, relapses have been documented  .
The diagnosis of erysipeloid may be difficult to obtain without a proper patient history and a thorough examination of the wound. Firstly, a detailed interview with the patient about his/her occupation and possible animal contact, as well as recent injury to the skin is an essential step in order to suspect Erysipelothrix rhusiopathiae as a possible cause. Moreover, a detailed physical examination of the lesion can reveal key features of erysipeloid, and the diagnosis can often be made solely on clinical criteria supported by details from patient history . A confirmation of the pathogen, however, can only be obtained after microbiological testing. A viable sample for cultivation requires a full-thickness biopsy of the lesion (due to the fact that bacteria is located deep within the skin), but the results may be provided after at least 3 or more days . Visualization of thin, gram-positive rods is considered diagnostic, but gram stains and other cultivation methods frequently yield negative results . For this reason, the introduction of novel molecular techniques, such as polymerase chain reaction (PCR), is slowly being introduced into regular practice, since they can rapidly detect bacterial DNA .