Arcanobacterium infections

STEPHANIE SPECK

Bundeswehr Institute of Microbiology, Department of Virol­ogy and Rickettsiology, Munich, Germany

TABLE 37.4 Diseases associated with Arcanobacterium (modified after Jost & Billington, 2004)(⁶6).

Within the genus Arcanobacterium, seven species have been associated with a variety of suppurative infections in animals: Arcanobacterium pyogenes, A. phocae, A. plurani- malium, A. abortisuis, A. bialowiezense, A. bonasi and A. hippocoleae (Table 37.4). Arcanobacterium pyogenes was for­merly known as Actinomyces pyogenes and Corynebacterium pyogenes. Bacteria of these genera are pleomorphic Gram­positive, non-motile, facultatively anaerobic, oxidase­negative short rods.

With the exception of A. pyogenes, little is known about the Arcanobacterium spp. that infect animals. Arcanobacte- rium pyogenes is a widely distributed inhabitant of the mucous membranes of the upper respiratory, gastrointes­tinal and genital tracts. Infection often occurs following injury or a preceding infection. Arcanobacterium pyogenes infections have been described in a wide range of mammals, and the agent was isolated from some birds and reptiles. This bacterium is common in mixed infections and has a synergistic relationship with Fusobacterium necrophorum and possibly other anaerobic bacteria.

In domestic cattle, A. pyogenes can cause severe clinical mastitis. The agent is spread via contaminated objects or is transmitted by Hydrotea irritans and other species of fly. Uterine infections, resulting in severe endometritis and infertility, umbilical infections and seminal vesiculitis have also been described in ruminants and pigs. In liver abscesses in feedlot cattle, A. pyogenes is the second most commonly isolated agent.

Foot infection associated with A. pyogenes has been described in Spanish fallow deer (Dama dama) in the Sueve Regional Hunting Reserve.

Intracranial abscessation is a cause of mortality in white­tailed deer (Odocoileus υirginianus). Arcanobacterium pyo­genes, as well as other bacteria, are thought to enter via skin wounds or abrasions around the head, or injured/ fractured antler pedicles. Penetration of infection into the cranium may then occur through the suture between the parietal and frontal bones. Subcutaneous abscesses on the head or ears due to ticks, bacterial otitis provoked by ear mites, and intraspecific trauma were considered con­tributory to intracranial abscess formation¹-⁶⁸).

Arcanobacterium bialowiezense and A. bonasi have both been isolated from European bison (Bison bonasus bonasus) bulls at Bialowieza National Park, Poland. Both bacteria were obtained in mixed cultures from the prepuce and penis of individuals suffering from balanoposthitis. Neither healthy bulls nor female bison harboured A. bialowiezense and A. bonasi; hence, a possible role of both species in the pathogenesis of balanoposthitis in European bison is suggested¹-⁶⁹).

Arcanobacterium spp. with so far unknown pathological significance have also been recovered from marine mammals (Table 37.4).

Arcanobacterium pyogenes is one of the most common opportunistic pathogens in domestic ruminants and pigs, but may also act as primary pathogen. Following injury to the host, A. pyogenes can disseminate to cause a variety of infections. Haematogenous spread to several body sites results in abscess formation and suppurative conditions.

Arcanobacterium pyogenes infections in domestic and captive wild ungulate species are frequently found; however, cases in free-ranging wildlife are scarce and prob­ably under-recorded. Lesions may form in any organ system with clinical signs corresponding to the lesion and the host’s immune response. Often no specific clinical signs are associated with A. pyogenes infection. In conjunc­tion with foot infection in fallow deer, unilateral swelling of extremities and suppurative tissue infection at the coronary band was observed. Radiography revealed slight to significant soft tissue swelling, loss of bone, severe periostal reaction and degenerative joint disease ⁽⁶⁷⁾. Animals with intracranial abscesses may show signs of incoordina­tion, blindness, profound depression, torticollis and circling⁽⁶⁸⁾.

Local abscess formation is often seen at necropsy. Exam­ination of affected white-tailed deer revealed necrosis, erosion and pitting of cranial bones. Lesions occurred on the external surfaces of the parietal and frontal bones, usually on or near the antler pedicles. Abscesses (1—3 mm in diameter) contained viscous pus, and were surrounded by an intense inflammatory reaction.

Gram-stained smears of pus or mastitic milk reveal small, highly pleomorphic, Gram-positive rods that occur singly, in pairs (V, T and palisade formations) or in clusters.

Arcanobacteria grow aerobically at 37°C on Columbia agar supplemented with 5% sheep blood.

I n wildlife, Arcanobacterium infection occurs sporadi­cally in individuals. A high density of male deer could be a factor that increases stress and territorial fights, especially during the breeding season, thus facilitating the occur­rence of abscess formation associated with injured body sites.