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For many years, Erysipelothrix rhusiopathiae has been known to be the causative agent of the occupationally related infection erysipeloid. A survey of the distribution of Erysipelothrix spp. in 19 Australasian seafoods was conducted, and methodologies for the detection of Erysipelothrix spp. were evaluated. Twenty-one Erysipelothrix spp. were isolated from 52 seafood parts. Primary isolation of Erysipelothrix spp. was most efficiently achieved with brain heart infusion broth enrichment followed by subculture onto a selective brain heart infusion agar containing kanamycin, neomycin, and vancomycin after 48 h of incubation. Selective tryptic soy broth, with 48 h of incubation, was the best culture method for the detection of Erysipelothrix spp. with PCR. PCR detection was 50% more sensitive than culture. E. rhusiopathiae was isolated from a variety of different fish, cephalopods, and crustaceans, including a Western rock lobster (Panulirus cygnus). There was no significant correlation between the origin of the seafoods tested and the distribution of E. rhusiopathiae. An organism indistinguishable from Erysipelothrix tonsillarum was isolated for the first time from an Australian oyster and a silver bream. Overall, Erysipelothrix spp. were widely distributed in Australasian seafoods, illustrating the potential for erysipeloidlike infections in fishermen.

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Erysipelothrix rhusiopathiae is pathogenic for both animals and humans, causing erysipelas in swine and erysipeloid in humans. In swine, disease may be either acute or chronic, resulting in the development of arthritis and endocarditis. In Japan, erysipelas remains an animal hygiene problem causing great economic loss as infected swine are disused. Human infection closely resembles that seen in swine, with both acute and chronic forms also. The most common presentation is erysipeloid, a localized cutaneous infection. In Western Australia, an erysipeloid-like infection referred to as "crayfish poisoning" occurs in lobster fishermen and handlers. A second type of presentation is a generalized cutaneous form involving lesions that progress from the initial site of infection or appear in remote areas. The third and most serious form of disease is a septicemia that is almost always linked to endocarditis. The mortality rate in Erysipelothrix endocarditis is still high (38%) and can be explained by the use of vancomycin (to which Erysipelothrix spp. are inherently resistant) as empirical therapy. Therefore, it is critical to have an early diagnosis of E. rhusiopathiae infection.Unfortunately, several problems exist with the diagnosis of E. rhusiopathiae infections by conventional cultural procedures, and these infections are often incorrectly diagnosed. First, because of their very small colony size and slow growth rates, it is difficult to isolate E. rhusiopathiae from heavily contaminated specimens. Various selective media have been described to improve the isolation of E. rhusiopathiae from contaminated specimens; however, not all contaminants are inhibited. The development of two polymerase chain reaction (PCR) methods has created an opportunity to greatly improve the efficiency with which these organisms are detected and identified. Makino et al. designed a PCR method that amplifies a 407-bp DNA fragment derived from the 16S rRNA coding sequence. The primers in this method are specific for the genus Erysipelothrix and do not differentiate between the species. A second set of primers designed by Shimoji et al. amplifies a 937-bp DNA fragment which is derived from a sequence associated with virulence of E. rhusiopathiae. These primers are specific for E. rhusiopathiae only. Shimoji et al. also utilized a selective enrichment medium based on tryptic soy broth containing ethidium bromide and sodium azide.